Merge branch 'main' into fix/1

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@modelcontextprotocol/sdk",
-  "version": "1.10.2",
+  "version": "1.11.1",
   "description": "Model Context Protocol implementation for TypeScript",
   "license": "MIT",
   "author": "Anthropic, PBC (https://anthropic.com)",

src/client/auth.test.ts

@@ -39,7 +39,7 @@ describe("OAuth Authorization", () => {
       const [url, options] = calls[0];
       expect(url.toString()).toBe("https://auth.example.com/.well-known/oauth-authorization-server");
       expect(options.headers).toEqual({
-        "MCP-Protocol-Version": "2024-11-05"
+        "MCP-Protocol-Version": "2025-03-26"
       });
     });
 
@@ -478,4 +478,4 @@ describe("OAuth Authorization", () => {
       ).rejects.toThrow("Dynamic client registration failed");
     });
   });
-});
+});

src/client/index.test.ts

@@ -165,6 +165,194 @@ test("should reject unsupported protocol version", async () => {
   expect(clientTransport.close).toHaveBeenCalled();
 });
 
+test("should connect new client to old, supported server version", async () => {
+  const OLD_VERSION = SUPPORTED_PROTOCOL_VERSIONS[1];
+  const server = new Server(
+      {
+        name: "test server",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          resources: {},
+          tools: {},
+        },
+      },
+  );
+
+  server.setRequestHandler(InitializeRequestSchema, (_request) => ({
+    protocolVersion: OLD_VERSION,
+    capabilities: {
+      resources: {},
+      tools: {},
+    },
+    serverInfo: {
+      name: "old server",
+      version: "1.0",
+    },
+  }));
+
+  server.setRequestHandler(ListResourcesRequestSchema, () => ({
+    resources: [],
+  }));
+
+  server.setRequestHandler(ListToolsRequestSchema, () => ({
+    tools: [],
+  }));
+
+  const [clientTransport, serverTransport] =
+      InMemoryTransport.createLinkedPair();
+
+  const client = new Client(
+      {
+        name: "new client",
+        version: "1.0",
+        protocolVersion: LATEST_PROTOCOL_VERSION,
+      },
+      {
+        capabilities: {
+          sampling: {},
+        },
+        enforceStrictCapabilities: true,
+      },
+  );
+
+  await Promise.all([
+    client.connect(clientTransport),
+    server.connect(serverTransport),
+  ]);
+
+  expect(client.getServerVersion()).toEqual({
+    name: "old server",
+    version: "1.0",
+  });
+});
+
+test("should negotiate version when client is old, and newer server supports its version", async () => {
+  const OLD_VERSION = SUPPORTED_PROTOCOL_VERSIONS[1];
+  const server = new Server(
+      {
+        name: "new server",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          resources: {},
+          tools: {},
+        },
+      },
+  );
+
+  server.setRequestHandler(InitializeRequestSchema, (_request) => ({
+    protocolVersion: LATEST_PROTOCOL_VERSION,
+    capabilities: {
+      resources: {},
+      tools: {},
+    },
+    serverInfo: {
+      name: "new server",
+      version: "1.0",
+    },
+  }));
+
+  server.setRequestHandler(ListResourcesRequestSchema, () => ({
+    resources: [],
+  }));
+
+  server.setRequestHandler(ListToolsRequestSchema, () => ({
+    tools: [],
+  }));
+
+  const [clientTransport, serverTransport] =
+      InMemoryTransport.createLinkedPair();
+
+  const client = new Client(
+      {
+        name: "old client",
+        version: "1.0",
+        protocolVersion: OLD_VERSION,
+      },
+      {
+        capabilities: {
+          sampling: {},
+        },
+        enforceStrictCapabilities: true,
+      },
+  );
+
+  await Promise.all([
+    client.connect(clientTransport),
+    server.connect(serverTransport),
+  ]);
+
+  expect(client.getServerVersion()).toEqual({
+    name: "new server",
+    version: "1.0",
+  });
+});
+
+test("should throw when client is old, and server doesn't support its version", async () => {
+  const OLD_VERSION = SUPPORTED_PROTOCOL_VERSIONS[1];
+  const FUTURE_VERSION = "FUTURE_VERSION";
+  const server = new Server(
+      {
+        name: "new server",
+        version: "1.0",
+      },
+      {
+        capabilities: {
+          resources: {},
+          tools: {},
+        },
+      },
+  );
+
+  server.setRequestHandler(InitializeRequestSchema, (_request) => ({
+    protocolVersion: FUTURE_VERSION,
+    capabilities: {
+      resources: {},
+      tools: {},
+    },
+    serverInfo: {
+      name: "new server",
+      version: "1.0",
+    },
+  }));
+
+  server.setRequestHandler(ListResourcesRequestSchema, () => ({
+    resources: [],
+  }));
+
+  server.setRequestHandler(ListToolsRequestSchema, () => ({
+    tools: [],
+  }));
+
+  const [clientTransport, serverTransport] =
+      InMemoryTransport.createLinkedPair();
+
+  const client = new Client(
+      {
+        name: "old client",
+        version: "1.0",
+        protocolVersion: OLD_VERSION,
+      },
+      {
+        capabilities: {
+          sampling: {},
+        },
+        enforceStrictCapabilities: true,
+      },
+  );
+
+  await Promise.all([
+    expect(client.connect(clientTransport)).rejects.toThrow(
+        "Server's protocol version is not supported: FUTURE_VERSION"
+    ),
+    server.connect(serverTransport),
+  ]);
+
+});
+
 test("should respect server capabilities", async () => {
   const server = new Server(
     {

src/client/stdio.ts

@@ -1,7 +1,7 @@
 import { ChildProcess, IOType } from "node:child_process";
 import spawn from "cross-spawn";
 import process from "node:process";
-import { Stream } from "node:stream";
+import { Stream, PassThrough } from "node:stream";
 import { ReadBuffer, serializeMessage } from "../shared/stdio.js";
 import { Transport } from "../shared/transport.js";
 import { JSONRPCMessage } from "../types.js";
@@ -93,6 +93,7 @@ export class StdioClientTransport implements Transport {
   private _abortController: AbortController = new AbortController();
   private _readBuffer: ReadBuffer = new ReadBuffer();
   private _serverParams: StdioServerParameters;
+  private _stderrStream: PassThrough | null = null;
 
   onclose?: () => void;
   onerror?: (error: Error) => void;
@@ -100,6 +101,9 @@ export class StdioClientTransport implements Transport {
 
   constructor(server: StdioServerParameters) {
     this._serverParams = server;
+    if (server.stderr === "pipe" || server.stderr === "overlapped") {
+      this._stderrStream = new PassThrough();
+    }
   }
 
   /**
@@ -162,15 +166,25 @@ export class StdioClientTransport implements Transport {
       this._process.stdout?.on("error", (error) => {
         this.onerror?.(error);
       });
+
+      if (this._stderrStream && this._process.stderr) {
+        this._process.stderr.pipe(this._stderrStream);
+      }
     });
   }
 
   /**
    * The stderr stream of the child process, if `StdioServerParameters.stderr` was set to "pipe" or "overlapped".
    *
-   * This is only available after the process has been started.
+   * If stderr piping was requested, a PassThrough stream is returned _immediately_, allowing callers to
+   * attach listeners before the start method is invoked. This prevents loss of any early
+   * error output emitted by the child process.
    */
   get stderr(): Stream | null {
+    if (this._stderrStream) {
+      return this._stderrStream;
+    }
+
     return this._process?.stderr ?? null;
   }
 

src/server/mcp.test.ts

@@ -622,6 +622,53 @@ describe("tool()", () => {
     });
   });
 
+  test("should register tool with description, empty params, and annotations", async () => {
+    const mcpServer = new McpServer({
+      name: "test server",
+      version: "1.0",
+    });
+    const client = new Client({
+      name: "test client",
+      version: "1.0",
+    });
+
+    mcpServer.tool(
+      "test", 
+      "A tool with everything but empty params",
+      {},
+      { title: "Complete Test Tool with empty params", readOnlyHint: true, openWorldHint: false },
+      async () => ({
+        content: [{ type: "text", text: "Test response" }]
+      })
+    );
+
+    const [clientTransport, serverTransport] =
+      InMemoryTransport.createLinkedPair();
+
+    await Promise.all([
+      client.connect(clientTransport),
+      mcpServer.server.connect(serverTransport),
+    ]);
+
+    const result = await client.request(
+      { method: "tools/list" },
+      ListToolsResultSchema,
+    );
+
+    expect(result.tools).toHaveLength(1);
+    expect(result.tools[0].name).toBe("test");
+    expect(result.tools[0].description).toBe("A tool with everything but empty params");
+    expect(result.tools[0].inputSchema).toMatchObject({
+      type: "object",
+      properties: {}
+    });
+    expect(result.tools[0].annotations).toEqual({ 
+      title: "Complete Test Tool with empty params", 
+      readOnlyHint: true,
+      openWorldHint: false
+    });
+  });
+
   test("should validate tool args", async () => {
     const mcpServer = new McpServer({
       name: "test server",

src/server/mcp.ts

@@ -663,8 +663,11 @@ export class McpServer {
     // Helper to check if an object is a Zod schema (ZodRawShape)
     const isZodRawShape = (obj: unknown): obj is ZodRawShape => {
       if (typeof obj !== "object" || obj === null) return false;
-      // Check that at least one property is a ZodType instance
-      return Object.values(obj as object).some(v => v instanceof ZodType);
+
+      const isEmptyObject = z.object({}).strict().safeParse(obj).success;
+
+      // Check if object is empty or at least one property is a ZodType instance
+      return isEmptyObject || Object.values(obj as object).some(v => v instanceof ZodType);
     };
 
     let description: string | undefined;

src/types.test.ts

@@ -0,0 +1,17 @@
+import { LATEST_PROTOCOL_VERSION, SUPPORTED_PROTOCOL_VERSIONS } from "./types.js";
+
+describe("Types", () => {
+
+    test("should have correct latest protocol version", () => {
+        expect(LATEST_PROTOCOL_VERSION).toBeDefined();
+        expect(LATEST_PROTOCOL_VERSION).toBe("2025-03-26");
+    });
+    test("should have correct supported protocol versions", () => {
+        expect(SUPPORTED_PROTOCOL_VERSIONS).toBeDefined();
+        expect(SUPPORTED_PROTOCOL_VERSIONS).toBeInstanceOf(Array);
+        expect(SUPPORTED_PROTOCOL_VERSIONS).toContain(LATEST_PROTOCOL_VERSION);
+        expect(SUPPORTED_PROTOCOL_VERSIONS).toContain("2024-11-05");
+        expect(SUPPORTED_PROTOCOL_VERSIONS).toContain("2024-10-07");
+    });
+
+});

src/types.ts

@@ -1,8 +1,9 @@
 import { z, ZodTypeAny } from "zod";
 
-export const LATEST_PROTOCOL_VERSION = "2024-11-05";
+export const LATEST_PROTOCOL_VERSION = "2025-03-26";
 export const SUPPORTED_PROTOCOL_VERSIONS = [
   LATEST_PROTOCOL_VERSION,
+  "2024-11-05",
   "2024-10-07",
 ];
 
@@ -754,11 +755,11 @@ export const PromptListChangedNotificationSchema = NotificationSchema.extend({
 /* Tools */
 /**
  * Additional properties describing a Tool to clients.
- * 
- * NOTE: all properties in ToolAnnotations are **hints**. 
- * They are not guaranteed to provide a faithful description of 
+ *
+ * NOTE: all properties in ToolAnnotations are **hints**.
+ * They are not guaranteed to provide a faithful description of
  * tool behavior (including descriptive properties like `title`).
- * 
+ *
  * Clients should never make tool use decisions based on ToolAnnotations
  * received from untrusted servers.
  */
@@ -771,7 +772,7 @@ export const ToolAnnotationsSchema = z
 
     /**
      * If true, the tool does not modify its environment.
-     * 
+     *
      * Default: false
      */
     readOnlyHint: z.optional(z.boolean()),
@@ -779,19 +780,19 @@ export const ToolAnnotationsSchema = z
     /**
      * If true, the tool may perform destructive updates to its environment.
      * If false, the tool performs only additive updates.
-     * 
+     *
      * (This property is meaningful only when `readOnlyHint == false`)
-     * 
+     *
      * Default: true
      */
     destructiveHint: z.optional(z.boolean()),
 
     /**
-     * If true, calling the tool repeatedly with the same arguments 
+     * If true, calling the tool repeatedly with the same arguments
      * will have no additional effect on the its environment.
-     * 
+     *
      * (This property is meaningful only when `readOnlyHint == false`)
-     * 
+     *
      * Default: false
      */
     idempotentHint: z.optional(z.boolean()),
@@ -801,7 +802,7 @@ export const ToolAnnotationsSchema = z
      * entities. If false, the tool's domain of interaction is closed.
      * For example, the world of a web search tool is open, whereas that
      * of a memory tool is not.
-     * 
+     *
      * Default: true
      */
     openWorldHint: z.optional(z.boolean()),