feat: add default value support to elicitation schemas (SEP-1034)

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/src/model/elicitation_schema.rs

@@ -108,6 +108,10 @@ pub struct StringSchema {
  /// String format - limited to: "email", "uri", "date", "date-time"
  #[serde(skip_serializing_if = "Option::is_none")]
  pub format: Option<StringFormat>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<Cow<'static, str>>,
 }
 
 impl Default for StringSchema {
@@ -119,6 +123,7 @@ impl Default for StringSchema {
  min_length: None,
  max_length: None,
  format: None,
+ default: None,
  }
  }
 }
@@ -208,6 +213,12 @@ impl StringSchema {
  self.format = Some(format);
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: impl Into<Cow<'static, str>>) -> Self {
+ self.default = Some(default.into());
+ self
+ }
 }
 
 // =============================================================================
@@ -241,6 +252,10 @@ pub struct NumberSchema {
  /// Maximum value (inclusive)
  #[serde(skip_serializing_if = "Option::is_none")]
  pub maximum: Option<f64>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<f64>,
 }
 
 impl Default for NumberSchema {
@@ -251,6 +266,7 @@ impl Default for NumberSchema {
  description: None,
  minimum: None,
  maximum: None,
+ default: None,
  }
  }
 }
@@ -302,6 +318,12 @@ impl NumberSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: f64) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -491,6 +513,10 @@ pub struct EnumSchema {
  /// Human-readable description
  #[serde(skip_serializing_if = "Option::is_none")]
  pub description: Option<Cow<'static, str>>,
+
+ /// Default value
+ #[serde(skip_serializing_if = "Option::is_none")]
+ pub default: Option<String>,
 }
 
 impl EnumSchema {
@@ -502,6 +528,7 @@ impl EnumSchema {
  enum_names: None,
  title: None,
  description: None,
+ default: None,
  }
  }
 
@@ -522,6 +549,12 @@ impl EnumSchema {
  self.description = Some(description.into());
  self
  }
+
+ /// Set default value
+ pub fn with_default(mut self, default: String) -> Self {
+ self.default = Some(default);
+ self
+ }
 }
 
 // =============================================================================
@@ -1177,4 +1210,114 @@ mod tests {
  assert!(result.is_err());
  assert_eq!(result.unwrap_err(), "minimum must be <= maximum");
  }
+
+ #[test]
+ fn test_string_schema_with_default() {
+ let schema = StringSchema::new()
+ .with_default("example@test.com")
+ .description("Email with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["default"], "example@test.com");
+ assert_eq!(json["description"], "Email with default");
+ }
+
+ #[test]
+ fn test_string_schema_without_default() {
+ let schema = StringSchema::new().description("Email without default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_number_schema_with_default() {
+ let schema = NumberSchema::new()
+ .range(0.0, 100.0)
+ .with_default(50.0)
+ .description("Percentage with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert_eq!(json["default"], 50.0);
+ assert_eq!(json["minimum"], 0.0);
+ assert_eq!(json["maximum"], 100.0);
+ }
+
+ #[test]
+ fn test_number_schema_without_default() {
+ let schema = NumberSchema::new().range(0.0, 100.0);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "number");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_enum_schema_with_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string(), "CA".to_string()])
+ .with_default("US".to_string())
+ .description("Country with default");
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert_eq!(json["enum"], json!(["US", "UK", "CA"]));
+ assert_eq!(json["default"], "US");
+ }
+
+ #[test]
+ fn test_enum_schema_without_default() {
+ let schema = EnumSchema::new(vec!["US".to_string(), "UK".to_string()]);
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "string");
+ assert!(json.get("default").is_none());
+ }
+
+ #[test]
+ fn test_elicitation_schema_with_defaults() {
+ let schema = ElicitationSchema::builder()
+ .required_string_with("name", |s| s.length(1, 100))
+ .property(
+ "email",
+ PrimitiveSchema::String(StringSchema::email().with_default("user@example.com")),
+ )
+ .property(
+ "age",
+ PrimitiveSchema::Number(NumberSchema::new().range(0.0, 150.0).with_default(25.0)),
+ )
+ .property(
+ "country",
+ PrimitiveSchema::Enum(
+ EnumSchema::new(vec!["US".to_string(), "UK".to_string()])
+ .with_default("US".to_string()),
+ ),
+ )
+ .description("User registration with defaults")
+ .build()
+ .unwrap();
+
+ let json = serde_json::to_value(&schema).unwrap();
+
+ assert_eq!(json["type"], "object");
+ assert_eq!(json["properties"]["email"]["default"], "user@example.com");
+ assert_eq!(json["properties"]["age"]["default"], 25.0);
+ assert_eq!(json["properties"]["country"]["default"], "US");
+ assert!(json["properties"]["name"].get("default").is_none());
+ }
+
+ #[test]
+ fn test_default_serialization_roundtrip() {
+ let original = StringSchema::new()
+ .with_default("test")
+ .description("Test schema");
+
+ let json = serde_json::to_value(&original).unwrap();
+ let deserialized: StringSchema = serde_json::from_value(json).unwrap();
+
+ assert_eq!(original, deserialized);
+ assert_eq!(deserialized.default, Some(Cow::Borrowed("test")));
+ }
 }

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [

crates/rmcp/tests/test_message_schema/server_json_rpc_message_schema_current.json

@@ -667,6 +667,13 @@
  "description": "Schema definition for enum properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nEnums must have string type and can optionally include human-readable names.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -1320,6 +1327,14 @@
  "description": "Schema definition for number properties (floating-point).\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec.",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "number",
+ "null"
+ ],
+ "format": "double"
+ },
  "description": {
  "description": "Human-readable description",
  "type": [
@@ -2227,6 +2242,13 @@
  "description": "Schema definition for string properties.\n\nCompliant with MCP 2025-06-18 specification for elicitation schemas.\nSupports only the fields allowed by the MCP spec:\n- format limited to: \"email\", \"uri\", \"date\", \"date-time\"",
  "type": "object",
  "properties": {
+ "default": {
+ "description": "Default value",
+ "type": [
+ "string",
+ "null"
+ ]
+ },
  "description": {
  "description": "Human-readable description",
  "type": [