Add configurable JSON Schema target specification

- Add jsonSchemaSpec option to ServerOptions for OpenAI compatibility
- Support for specifying JSON Schema target (e.g., 'jsonSchema7')
- Use configured target in zodToJsonSchema calls in McpServer
- Defaults to 'jsonSchema7' for backward compatibility

Author: ashburnham

src/server/index.ts

@@ -37,6 +37,7 @@ import {
   LoggingLevelSchema
 } from "../types.js";
 import Ajv from "ajv";
+import type { Target } from "zod-to-json-schema";
 
 export type ServerOptions = ProtocolOptions & {
   /**
@@ -48,6 +49,11 @@ export type ServerOptions = ProtocolOptions & {
    * Optional instructions describing how to use the server and its features.
    */
   instructions?: string;
+
+  /**
+   * Optional spec for JSON Schema to allow fully compatible use with OpenAI endpoints.
+   */
+  jsonSchemaSpec?: Target;
 };
 
 /**
@@ -88,6 +94,7 @@ export class Server<
   private _clientVersion?: Implementation;
   private _capabilities: ServerCapabilities;
   private _instructions?: string;
+  public _jsonSchemaSpec?: Target = 'jsonSchema7';
 
   /**
    * Callback for when initialization has fully completed (i.e., the client has sent an `initialized` notification).
@@ -104,6 +111,7 @@ export class Server<
     super(options);
     this._capabilities = options?.capabilities ?? {};
     this._instructions = options?.instructions;
+    this._jsonSchemaSpec = options?.jsonSchemaSpec;
 
     this.setRequestHandler(InitializeRequestSchema, (request) =>
       this._oninitialize(request),

src/server/mcp.ts

@@ -119,6 +119,7 @@ export class McpServer {
               description: tool.description,
               inputSchema: tool.inputSchema
                 ? (zodToJsonSchema(tool.inputSchema, {
+                  target: this.server._jsonSchemaSpec,
                   strictUnions: true,
                 }) as Tool["inputSchema"])
                 : EMPTY_OBJECT_JSON_SCHEMA,