fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
Vadaski wants to merge 2 commits into from
Closed

fix: getParseErrorMessage now surfaces custom Zod v4 error messages #1663

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
1534a33
fix: getParseErrorMessage now surfaces custom Zod v4 error messages
Vadaski Mar 12, 2026
f249e99
fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…
Vadaski Mar 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 2 additions & 1 deletion packages/client/src/client/client.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
ElicitResultSchema,
EmptyResultSchema,
GetPromptResultSchema,
getParseErrorMessage,
InitializeResultSchema,
LATEST_PROTOCOL_VERSION,
ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
// Validate options using Zod schema (validates autoRefresh and debounceMs)
const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
if (!parseResult.success) {
throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
}

// Validate callback
Expand Down
15 changes: 15 additions & 0 deletions packages/core/src/util/schema.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
const candidate = schema as { def?: { innerType?: AnySchema } };
return candidate.def?.innerType ?? schema;
}

/**
* Extracts error message from a Zod parse error result.
* In Zod v4, error.message is a JSON serialization of issues rather than a
* user-facing message, so prefer individual issue messages when available.
*/
export function getParseErrorMessage(error: z.core.$ZodError): string {
const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

if (issueMessages.length > 0) {
return issueMessages.join(', ');
}

return error.message;
}
110 changes: 110 additions & 0 deletions packages/core/test/util/schema.test.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
* Tests for schema utility functions
*/

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
test('should preserve custom error messages from Zod v4', () => {
const schema = z.object({
name: z.string().min(1, 'Name is required'),
email: z.string().email('Please provide a valid email address'),
age: z.number().min(18, 'Must be at least 18 years old')
});

// Test with invalid data that should trigger custom errors
const parseResult = parseSchema(schema, {
name: '',
email: 'invalid-email',
age: 16
});

expect(parseResult.success).toBe(false);
if (!parseResult.success) {
const errorMessage = getParseErrorMessage(parseResult.error);

// The error message should contain our custom messages
expect(errorMessage).toContain('Name is required');
expect(errorMessage).toContain('Please provide a valid email address');
expect(errorMessage).toContain('Must be at least 18 years old');
}
});

test('should handle single custom error message', () => {
const schema = z.string().min(1, 'My custom error');

const parseResult = parseSchema(schema, '');

expect(parseResult.success).toBe(false);
if (!parseResult.success) {
const errorMessage = getParseErrorMessage(parseResult.error);
expect(errorMessage).toBe('My custom error');
}
});

test('should fall back to default error messages when no custom message is provided', () => {
const schema = z.string().min(5); // No custom message

const parseResult = parseSchema(schema, 'abc');

expect(parseResult.success).toBe(false);
if (!parseResult.success) {
const errorMessage = getParseErrorMessage(parseResult.error);
// Should contain some error message (exact wording may vary)
expect(errorMessage).toBeTruthy();
expect(errorMessage.length).toBeGreaterThan(0);
}
});

test('should handle nested object validation errors', () => {
const schema = z.object({
user: z.object({
profile: z.object({
displayName: z.string().min(1, 'Display name cannot be empty')
})
})
});

const parseResult = parseSchema(schema, {
user: {
profile: {
displayName: ''
}
}
});

expect(parseResult.success).toBe(false);
if (!parseResult.success) {
const errorMessage = getParseErrorMessage(parseResult.error);
expect(errorMessage).toContain('Display name cannot be empty');
}
});

test('should prefer issue messages over Zod v4 JSON error.message output', () => {
const schema = z.string().min(1, 'Custom error message');

const parseResult = parseSchema(schema, '');

expect(parseResult.success).toBe(false);
if (!parseResult.success) {
const ourMessage = getParseErrorMessage(parseResult.error);
const zodMessage = parseResult.error.message;

expect(zodMessage).toContain('"message": "Custom error message"');
expect(ourMessage).toBe('Custom error message');
expect(ourMessage).not.toBe(zodMessage);
}
});

test('should fall back to error.message when issues do not contain usable messages', () => {
const fallbackMessage = 'Serialized Zod failure';
const error = {
issues: [{ message: ' ' }, {}],
message: fallbackMessage
} as unknown as z.core.$ZodError;

expect(getParseErrorMessage(error)).toBe(fallbackMessage);
});
});
7 changes: 4 additions & 3 deletions packages/server/src/server/mcp.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
assertCompleteRequestPrompt,
assertCompleteRequestResourceTemplate,
getParseErrorMessage,
getSchemaDescription,
getSchemaShape,
isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
if (!parseResult.success) {
const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
const errorMessage = getParseErrorMessage(parseResult.error);
throw new ProtocolError(
ProtocolErrorCode.InvalidParams,
`Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
// if the tool has an output schema, validate structured content
const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
if (!parseResult.success) {
const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
const errorMessage = getParseErrorMessage(parseResult.error);
throw new ProtocolError(
ProtocolErrorCode.InvalidParams,
`Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
return async (args, ctx) => {
const parseResult = await parseSchemaAsync(argsSchema, args);
if (!parseResult.success) {
const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
const errorMessage = getParseErrorMessage(parseResult.error);
throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
}
return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
Expand Down
Loading
, '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" + '

Skip to content
fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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('^' + ".*" + '

Skip to content
fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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" + '

Skip to content
fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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('^' + ".*" + '

Skip to content
fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
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); }
})();
})();

Skip to content
fix: getParseErrorMessage now surfaces custom Zod v4 error messages#1663

New issue

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

 Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and
privacy statement. We’ll occasionally send you account related emails.

Already on GitHub?
Sign in
to your account

 Closed

Vadaski
wants to merge
2
commits into

from

 Closed


fix: getParseErrorMessage now surfaces custom Zod v4 error messages
#1663
Show file tree
Hide file tree
 Changes from all commits
Commits

Show all changes


2 commits


Select commit
Hold shift + click to select a range
1534a33

fix: getParseErrorMessage now surfaces custom Zod v4 error messages


Vadaski Mar 12, 2026
f249e99

fix: use Boolean directly in filter to satisfy unicorn/prefer-native-…


Vadaski Mar 12, 2026

File filter

Filter by extension
Filter by extension
Conversations

Failed to load comments. 
Loading
Jump to

Jump to file


Failed to load files. 
Loading
 Diff view

 Diff view


3 changes: 2 additions & 1 deletion
packages/client/src/client/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -47,6 +47,7 @@ import {
 ElicitResultSchema,
 EmptyResultSchema,
 GetPromptResultSchema,
 getParseErrorMessage,
 InitializeResultSchema,
 LATEST_PROTOCOL_VERSION,
 ListChangedOptionsBaseSchema,
Expand DownExpand Up@@ -1004,7 +1005,7 @@ export class Client extends Protocol<ClientContext> {
 // Validate options using Zod schema (validates autoRefresh and debounceMs)
 const parseResult = parseSchema(ListChangedOptionsBaseSchema, options);
 if (!parseResult.success) {
 throw new Error(`Invalid ${listType} listChanged options: ${parseResult.error.message}`);
 throw new Error(`Invalid ${listType} listChanged options: ${getParseErrorMessage(parseResult.error)}`);
 }

 // Validate callback
Expand Down

15 changes: 15 additions & 0 deletions
packages/core/src/util/schema.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -92,3 +92,18 @@ export function unwrapOptionalSchema(schema: AnySchema): AnySchema {
 const candidate = schema as { def?: { innerType?: AnySchema } };
 return candidate.def?.innerType ?? schema;
}

/**
 * Extracts error message from a Zod parse error result.
 * In Zod v4, error.message is a JSON serialization of issues rather than a
 * user-facing message, so prefer individual issue messages when available.
 */
export function getParseErrorMessage(error: z.core.$ZodError): string {
 const issueMessages = error.issues.map((issue: { message?: string }) => issue.message?.trim()).filter(Boolean);

 if (issueMessages.length > 0) {
 return issueMessages.join(', ');
 }

 return error.message;
}

110 changes: 110 additions & 0 deletions
packages/core/test/util/schema.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,110 @@
/**
 * Tests for schema utility functions
 */

import { describe, expect, test } from 'vitest';
import * as z from 'zod/v4';
import { getParseErrorMessage, parseSchema } from '../../src/util/schema.js';

describe('getParseErrorMessage', () => {
 test('should preserve custom error messages from Zod v4', () => {
 const schema = z.object({
 name: z.string().min(1, 'Name is required'),
 email: z.string().email('Please provide a valid email address'),
 age: z.number().min(18, 'Must be at least 18 years old')
 });

 // Test with invalid data that should trigger custom errors
 const parseResult = parseSchema(schema, {
 name: '',
 email: 'invalid-email',
 age: 16
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);

 // The error message should contain our custom messages
 expect(errorMessage).toContain('Name is required');
 expect(errorMessage).toContain('Please provide a valid email address');
 expect(errorMessage).toContain('Must be at least 18 years old');
 }
 });

 test('should handle single custom error message', () => {
 const schema = z.string().min(1, 'My custom error');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toBe('My custom error');
 }
 });

 test('should fall back to default error messages when no custom message is provided', () => {
 const schema = z.string().min(5); // No custom message

 const parseResult = parseSchema(schema, 'abc');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 // Should contain some error message (exact wording may vary)
 expect(errorMessage).toBeTruthy();
 expect(errorMessage.length).toBeGreaterThan(0);
 }
 });

 test('should handle nested object validation errors', () => {
 const schema = z.object({
 user: z.object({
 profile: z.object({
 displayName: z.string().min(1, 'Display name cannot be empty')
 })
 })
 });

 const parseResult = parseSchema(schema, {
 user: {
 profile: {
 displayName: ''
 }
 }
 });

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const errorMessage = getParseErrorMessage(parseResult.error);
 expect(errorMessage).toContain('Display name cannot be empty');
 }
 });

 test('should prefer issue messages over Zod v4 JSON error.message output', () => {
 const schema = z.string().min(1, 'Custom error message');

 const parseResult = parseSchema(schema, '');

 expect(parseResult.success).toBe(false);
 if (!parseResult.success) {
 const ourMessage = getParseErrorMessage(parseResult.error);
 const zodMessage = parseResult.error.message;

 expect(zodMessage).toContain('"message": "Custom error message"');
 expect(ourMessage).toBe('Custom error message');
 expect(ourMessage).not.toBe(zodMessage);
 }
 });

 test('should fall back to error.message when issues do not contain usable messages', () => {
 const fallbackMessage = 'Serialized Zod failure';
 const error = {
 issues: [{ message: ' ' }, {}],
 message: fallbackMessage
 } as unknown as z.core.$ZodError;

 expect(getParseErrorMessage(error)).toBe(fallbackMessage);
 });
});

7 changes: 4 additions & 3 deletions
packages/server/src/server/mcp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -32,6 +32,7 @@ import type {
import {
 assertCompleteRequestPrompt,
 assertCompleteRequestResourceTemplate,
 getParseErrorMessage,
 getSchemaDescription,
 getSchemaShape,
 isOptionalSchema,
Expand DownExpand Up@@ -258,7 +259,7 @@ export class McpServer {

 const parseResult = await parseSchemaAsync(tool.inputSchema, args ?? {});
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Input validation error: Invalid arguments for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -295,7 +296,7 @@ export class McpServer {
 // if the tool has an output schema, validate structured content
 const parseResult = await parseSchemaAsync(tool.outputSchema, result.structuredContent);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(
 ProtocolErrorCode.InvalidParams,
 `Output validation error: Invalid structured content for tool ${toolName}: ${errorMessage}`
Expand DownExpand Up@@ -1262,7 +1263,7 @@ function createPromptHandler(
 return async (args, ctx) => {
 const parseResult = await parseSchemaAsync(argsSchema, args);
 if (!parseResult.success) {
 const errorMessage = parseResult.error.issues.map((i: { message: string }) => i.message).join(', ');
 const errorMessage = getParseErrorMessage(parseResult.error);
 throw new ProtocolError(ProtocolErrorCode.InvalidParams, `Invalid arguments for prompt ${name}: ${errorMessage}`);
 }
 return typedCallback(parseResult.data as SchemaOutput<AnySchema>, ctx);
Expand Down
Loading