fix: elicitation json schema validation in Cloudflare Worker

package.json

@@ -63,7 +63,7 @@
         "client": "tsx src/cli.ts client"
     },
     "dependencies": {
-        "ajv": "^6.12.6",
+        "@cfworker/json-schema": "^4.1.1",
         "content-type": "^1.0.5",
         "cors": "^2.8.5",
         "cross-spawn": "^7.0.5",
@@ -91,8 +91,8 @@
         "@types/ws": "^8.5.12",
         "eslint": "^9.8.0",
         "eslint-config-prettier": "^10.1.8",
-        "prettier": "3.6.2",
         "jest": "^29.7.0",
+        "prettier": "3.6.2",
         "supertest": "^7.0.0",
         "ts-jest": "^29.2.4",
         "tsx": "^4.16.5",

src/client/index.ts

@@ -38,8 +38,7 @@ import {
     ErrorCode,
     McpError
 } from '../types.js';
-import Ajv from 'ajv';
-import type { ValidateFunction } from 'ajv';
+import { Validator, Schema } from '@cfworker/json-schema';
 
 export type ClientOptions = ProtocolOptions & {
     /**
@@ -82,8 +81,7 @@ export class Client<
     private _serverVersion?: Implementation;
     private _capabilities: ClientCapabilities;
     private _instructions?: string;
-    private _cachedToolOutputValidators: Map<string, ValidateFunction> = new Map();
-    private _ajv: InstanceType<typeof Ajv>;
+    private _cachedToolOutputValidators: Map<string, Validator> = new Map();
 
     /**
      * Initializes this client with the given name and version information.
@@ -94,7 +92,6 @@ export class Client<
     ) {
         super(options);
         this._capabilities = options?.capabilities ?? {};
-        this._ajv = new Ajv();
     }
 
     /**
@@ -348,12 +345,14 @@ export class Client<
             if (result.structuredContent) {
                 try {
                     // Validate the structured content (which is already an object) against the schema
-                    const isValid = validator(result.structuredContent);
+                    const validationResult = validator.validate(result.structuredContent);
+
+                    if (!validationResult.valid) {
+                        const errorMessages = validationResult.errors.map(error => `${error.instanceLocation}: ${error.error}`).join('; ');
 
-                    if (!isValid) {
                         throw new McpError(
                             ErrorCode.InvalidParams,
-                            `Structured content does not match the tool's output schema: ${this._ajv.errorsText(validator.errors)}`
+                            `Structured content does not match the tool's output schema: ${errorMessages}`
                         );
                     }
                 } catch (error) {
@@ -375,10 +374,10 @@ export class Client<
         this._cachedToolOutputValidators.clear();
 
         for (const tool of tools) {
-            // If the tool has an outputSchema, create and cache the Ajv validator
+            // If the tool has an outputSchema, create and cache the validator
             if (tool.outputSchema) {
                 try {
-                    const validator = this._ajv.compile(tool.outputSchema);
+                    const validator = new Validator(tool.outputSchema as Schema, '2020-12');
                     this._cachedToolOutputValidators.set(tool.name, validator);
                 } catch {
                     // Ignore schema compilation errors
@@ -387,7 +386,7 @@ export class Client<
         }
     }
 
-    private getToolOutputValidator(toolName: string): ValidateFunction | undefined {
+    private getToolOutputValidator(toolName: string): Validator | undefined {
         return this._cachedToolOutputValidators.get(toolName);
     }