fix: support valid JSON value in tool structured content output#551

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tzolov merged 1 commit into from
Sep 15, 2025
Merged

fix: support valid JSON value in tool structured content output #551

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76 changes: 66 additions & 10 deletions mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

// In WebMVC, structured content is returned properly
if (response.structuredContent() != null) {
assertThat(response.structuredContent()).containsEntry("result", 5.0)
assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
.containsEntry("operation", "2 + 3")
.containsEntry("timestamp", "2024-01-01T10:00:00Z");
}
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
}

@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
@ValueSource(strings = { "httpclient" })
void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

// Create a tool with output schema that returns an array of objects
Map<String, Object> outputSchema = Map
.of( // @formatter:off
"type", "array",
"items", Map.of(
"type", "object",
"properties", Map.of(
"name", Map.of("type", "string"),
"age", Map.of("type", "number")),
"required", List.of("name", "age"))); // @formatter:on

Tool calculatorTool = Tool.builder()
.name("getMembers")
.description("Returns a list of members")
.outputSchema(outputSchema)
.build();

McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
.tool(calculatorTool)
.callHandler((exchange, request) -> {
return CallToolResult.builder()
.structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
.build();
})
.build();

var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
.capabilities(ServerCapabilities.builder().tools(true).build())
.tools(tool)
.build();

try (var mcpClient = clientBuilder.build()) {
assertThat(mcpClient.initialize()).isNotNull();

// Call tool with valid structured output of type array
CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

assertThat(response).isNotNull();
assertThat(response.isError()).isFalse();

assertThat(response.structuredContent()).isNotNull();
assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
.isArray()
.hasSize(2)
.containsExactlyInAnyOrder(json("""
{"name":"John","age":30}"""), json("""
{"name":"Peter","age":25}"""));
}
finally {
mcpServer.closeGracefully();
}
}

@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient" })
void testStructuredOutputWithInHandlerError(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
.outputSchema(outputSchema)
.build();

// Handler that throws an exception to simulate an error
// Handler that returns an error result
McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
.tool(calculatorTool)
.callHandler((exchange, request) -> {

return CallToolResult.builder()
.isError(true)
.content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
.build();
})
.callHandler((exchange, request) -> CallToolResult.builder()
.isError(true)
.content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
.build())
.build();

var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down
63 changes: 61 additions & 2 deletions mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
// ---------------------------------------
// Tool Structured Output Schema Tests
// ---------------------------------------

@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

// In WebMVC, structured content is returned properly
if (response.structuredContent() != null) {
assertThat(response.structuredContent()).containsEntry("result", 5.0)
assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
.containsEntry("operation", "2 + 3")
.containsEntry("timestamp", "2024-01-01T10:00:00Z");
}
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
}
}

@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
var clientBuilder = clientBuilders.get(clientType);

// Create a tool with output schema that returns an array of objects
Map<String, Object> outputSchema = Map
.of( // @formatter:off
"type", "array",
"items", Map.of(
"type", "object",
"properties", Map.of(
"name", Map.of("type", "string"),
"age", Map.of("type", "number")),
"required", List.of("name", "age"))); // @formatter:on

Tool calculatorTool = Tool.builder()
.name("getMembers")
.description("Returns a list of members")
.outputSchema(outputSchema)
.build();

McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
.builder()
.tool(calculatorTool)
.callHandler((exchange, request) -> {
return CallToolResult.builder()
.structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
.build();
})
.build();

var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
.capabilities(ServerCapabilities.builder().tools(true).build())
.tools(tool)
.build();

try (var mcpClient = clientBuilder.build()) {
assertThat(mcpClient.initialize()).isNotNull();

// Call tool with valid structured output of type array
CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

assertThat(response).isNotNull();
assertThat(response.isError()).isFalse();

assertThat(response.structuredContent()).isNotNull();
assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
.isArray()
.hasSize(2)
.containsExactlyInAnyOrder(json("""
{"name":"John","age":30}"""), json("""
{"name":"Peter","age":25}"""));
}
finally {
mcpServer.closeGracefully();
}
}

@ParameterizedTest(name = "{0} : {displayName} ")
@ValueSource(strings = { "httpclient", "webflux" })
void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down
20 changes: 10 additions & 10 deletions mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
// TextContent block.)
// https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
result.isError(), result.structuredContent());
return CallToolResult.builder()
.content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
.isError(result.isError())
.structuredContent(result.structuredContent())
.build();
}

return result;
Expand Down
7 changes: 5 additions & 2 deletions mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java
View file
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Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
// TextContent block.)
// https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
result.isError(), result.structuredContent());
return CallToolResult.builder()
.content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
.isError(result.isError())
.structuredContent(result.structuredContent())
.build();
}

return result;
Expand Down
2 changes: 1 addition & 1 deletion mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java
View file
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Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
}

@Override
public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

Assert.notNull(schema, "Schema must not be null");
Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down
2 changes: 1 addition & 1 deletion mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java
View file
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Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
* @return A ValidationResponse indicating whether the validation was successful or
* not.
*/
ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}
26 changes: 15 additions & 11 deletions mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java
View file
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Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
* Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
public record CallToolResult( // @formatter:off
@JsonProperty("content") List<Content> content,
@JsonProperty("isError") Boolean isError,
@JsonProperty("structuredContent") Map<String, Object> structuredContent,
@JsonProperty("structuredContent") Object structuredContent,
@JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

// backwards compatibility constructor
/**
* @deprecated use the builder instead.
*/
@Deprecated
public CallToolResult(List<Content> content, Boolean isError) {
this(content, isError, null, null);
this(content, isError, (Object) null, null);
}

// backwards compatibility constructor
/**
* @deprecated use the builder instead.
*/
@Deprecated
public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
this(content, isError, structuredContent, null);
}
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

private Boolean isError = false;

private Map<String, Object> structuredContent;
private Object structuredContent;

private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
return this;
}

public Builder structuredContent(Map<String, Object> structuredContent) {
public Builder structuredContent(Object structuredContent) {
Assert.notNull(structuredContent, "structuredContent must not be null");
this.structuredContent = structuredContent;
return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
* @return a new CallToolResult instance
*/
public CallToolResult build() {
return new CallToolResult(content, isError, structuredContent, meta);
return new CallToolResult(content, isError, (Object) structuredContent, meta);
}

}
Expand Down
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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fix: support valid JSON value in tool structured content output#551

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 Merged

tzolov
merged 1 commit into

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Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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fix: support valid JSON value in tool structured content output#551

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 Merged

tzolov
merged 1 commit into

from

Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix: support valid JSON value in tool structured content output#551

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Merged

tzolov
merged 1 commit into

from

Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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fix: support valid JSON value in tool structured content output#551

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 Merged

tzolov
merged 1 commit into

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Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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fix: support valid JSON value in tool structured content output#551

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tzolov
merged 1 commit into

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Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
fix: support valid JSON value in tool structured content output#551

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 Merged

tzolov
merged 1 commit into

from

Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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fix: support valid JSON value in tool structured content output#551

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 Merged

tzolov
merged 1 commit into

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Sep 15, 2025
 Merged


fix: support valid JSON value in tool structured content output
#551
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76 changes: 66 additions & 10 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1411,7 +1411,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -1433,7 +1433,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient" })
	void testStructuredOutputWithInHandlerError(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

Expand All@@ -1449,16 +1508,13 @@ void testStructuredOutputWithInHandlerError(String clientType) {
 .outputSchema(outputSchema)
 .build();

 // Handler that throws an exception to simulate an error
 // Handler that returns an error result
 McpServerFeatures.SyncToolSpecification tool = McpServerFeatures.SyncToolSpecification.builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {

 return CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build();
 })
 .callHandler((exchange, request) -> CallToolResult.builder()
 .isError(true)
 .content(List.of(new TextContent("Error calling tool: Simulated in-handler error")))
 .build())
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
Expand Down

63 changes: 61 additions & 2 deletions
mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

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Original file line numberDiff line numberDiff line change
Expand Up@@ -274,7 +274,6 @@ void testInitialize(String clientType) {
	// ---------------------------------------
	// Tool Structured Output Schema Tests
	// ---------------------------------------

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputValidationSuccess(String clientType) {
Expand DownExpand Up@@ -329,7 +328,7 @@ void testStructuredOutputValidationSuccess(String clientType) {

 // In WebMVC, structured content is returned properly
 if (response.structuredContent() != null) {
 assertThat(response.structuredContent()).containsEntry("result", 5.0)
 assertThat((Map<String, Object>) response.structuredContent()).containsEntry("result", 5.0)
 .containsEntry("operation", "2 + 3")
 .containsEntry("timestamp", "2024-01-01T10:00:00Z");
 }
Expand All@@ -350,6 +349,66 @@ void testStructuredOutputValidationSuccess(String clientType) {
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputOfObjectArrayValidationSuccess(String clientType) {
 var clientBuilder = clientBuilders.get(clientType);

 // Create a tool with output schema that returns an array of objects
 Map<String, Object> outputSchema = Map
 .of( // @formatter:off
 "type", "array",
 "items", Map.of(
 "type", "object",
 "properties", Map.of(
 "name", Map.of("type", "string"),
 "age", Map.of("type", "number")), 
 "required", List.of("name", "age"))); // @formatter:on

 Tool calculatorTool = Tool.builder()
 .name("getMembers")
 .description("Returns a list of members")
 .outputSchema(outputSchema)
 .build();

 McpStatelessServerFeatures.SyncToolSpecification tool = McpStatelessServerFeatures.SyncToolSpecification
 .builder()
 .tool(calculatorTool)
 .callHandler((exchange, request) -> {
 return CallToolResult.builder()
 .structuredContent(List.of(Map.of("name", "John", "age", 30), Map.of("name", "Peter", "age", 25)))
 .build();
 })
 .build();

 var mcpServer = prepareSyncServerBuilder().serverInfo("test-server", "1.0.0")
 .capabilities(ServerCapabilities.builder().tools(true).build())
 .tools(tool)
 .build();

 try (var mcpClient = clientBuilder.build()) {
 assertThat(mcpClient.initialize()).isNotNull();

 // Call tool with valid structured output of type array
 CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("getMembers", Map.of()));

 assertThat(response).isNotNull();
 assertThat(response.isError()).isFalse();

 assertThat(response.structuredContent()).isNotNull();
 assertThatJson(response.structuredContent()).when(Option.IGNORING_ARRAY_ORDER)
 .when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
 .isArray()
 .hasSize(2)
 .containsExactlyInAnyOrder(json("""
 {"name":"John","age":30}"""), json("""
 {"name":"Peter","age":25}"""));
 }
 finally {
 mcpServer.closeGracefully();
 }
	}

	@ParameterizedTest(name = "{0} : {displayName} ")
	@ValueSource(strings = { "httpclient", "webflux" })
	void testStructuredOutputWithInHandlerError(String clientType) {
Expand Down

20 changes: 10 additions & 10 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -15,15 +15,9 @@
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.spec.DefaultMcpStreamableServerSessionFactory;
import io.modelcontextprotocol.spec.JsonSchemaValidator;
import io.modelcontextprotocol.spec.McpClientSession;
import io.modelcontextprotocol.spec.McpError;
Expand All@@ -34,14 +28,17 @@
import io.modelcontextprotocol.spec.McpSchema.LoggingMessageNotification;
import io.modelcontextprotocol.spec.McpSchema.ResourceTemplate;
import io.modelcontextprotocol.spec.McpSchema.SetLevelRequest;
import io.modelcontextprotocol.spec.McpSchema.TextContent;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpServerSession;
import io.modelcontextprotocol.spec.McpServerTransportProvider;
import io.modelcontextprotocol.spec.McpServerTransportProviderBase;
import io.modelcontextprotocol.spec.McpStreamableServerTransportProvider;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DeafaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

Expand DownExpand Up@@ -420,8 +417,11 @@ public Mono<CallToolResult> apply(McpAsyncServerExchange exchange, McpSchema.Cal
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

7 changes: 5 additions & 2 deletions
mcp/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -293,8 +293,11 @@ public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchem
 // TextContent block.)
 // https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

 return new CallToolResult(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())),
 result.isError(), result.structuredContent());
 return CallToolResult.builder()
 .content(List.of(new McpSchema.TextContent(validation.jsonStructuredOutput())))
 .isError(result.isError())
 .structuredContent(result.structuredContent())
 .build();
 }

 return result;
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/DefaultJsonSchemaValidator.java

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -51,7 +51,7 @@ public DefaultJsonSchemaValidator(ObjectMapper objectMapper) {
	}

	@Override
	public ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent) {
	public ValidationResponse validate(Map<String, Object> schema, Object structuredContent) {

 Assert.notNull(schema, "Schema must not be null");
 Assert.notNull(structuredContent, "Structured content must not be null");
Expand Down

2 changes: 1 addition & 1 deletion
mcp/src/main/java/io/modelcontextprotocol/spec/JsonSchemaValidator.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -40,6 +40,6 @@ public static ValidationResponse asInvalid(String message) {
 * @return A ValidationResponse indicating whether the validation was successful or
 * not.
 */
	ValidationResponse validate(Map<String, Object> schema, Map<String, Object> structuredContent);
	ValidationResponse validate(Map<String, Object> schema, Object structuredContent);

}

26 changes: 15 additions & 11 deletions
mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,9 +11,6 @@
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
Expand All@@ -23,8 +20,9 @@
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.modelcontextprotocol.util.Assert;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Based on the <a href="http://www.jsonrpc.org/specification">JSON-RPC 2.0
Expand DownExpand Up@@ -1508,15 +1506,21 @@ public CallToolRequest build() {
	public record CallToolResult( // @formatter:off
 @JsonProperty("content") List<Content> content,
 @JsonProperty("isError") Boolean isError,
 @JsonProperty("structuredContent") Map<String, Object> structuredContent,
 @JsonProperty("structuredContent") Object structuredContent,
 @JsonProperty("_meta") Map<String, Object> meta) implements Result { // @formatter:on

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError) {
 this(content, isError, null, null);
 this(content, isError, (Object) null, null);
 }

 // backwards compatibility constructor
 /**
 * @deprecated use the builder instead.
 */
 @Deprecated
 public CallToolResult(List<Content> content, Boolean isError, Map<String, Object> structuredContent) {
 this(content, isError, structuredContent, null);
 }
Expand DownExpand Up@@ -1551,7 +1555,7 @@ public static class Builder {

 private Boolean isError = false;

 private Map<String, Object> structuredContent;
 private Object structuredContent;

 private Map<String, Object> meta;

Expand All@@ -1566,7 +1570,7 @@ public Builder content(List<Content> content) {
 return this;
 }

 public Builder structuredContent(Map<String, Object> structuredContent) {
 public Builder structuredContent(Object structuredContent) {
 Assert.notNull(structuredContent, "structuredContent must not be null");
 this.structuredContent = structuredContent;
 return this;
Expand DownExpand Up@@ -1644,7 +1648,7 @@ public Builder meta(Map<String, Object> meta) {
 * @return a new CallToolResult instance
 */
 public CallToolResult build() {
 return new CallToolResult(content, isError, structuredContent, meta);
 return new CallToolResult(content, isError, (Object) structuredContent, meta);
 }

 }
Expand Down
Loading