Merge branch 'main' into fix/1

Author: sunrabbit123

README.md

@@ -12,6 +12,7 @@
   - [Tools](#tools)
   - [Prompts](#prompts)
   - [Completions](#completions)
+  - [Sampling](#sampling)
 - [Running Your Server](#running-your-server)
   - [stdio](#stdio)
   - [Streamable HTTP](#streamable-http)
@@ -44,6 +45,8 @@ The Model Context Protocol allows applications to provide context for LLMs in a
 npm install @modelcontextprotocol/sdk
 ```
 
+> ⚠️ MCP requires Node v18.x up to work fine.
+
 ## Quick Start
 
 Let's create a simple MCP server that exposes a calculator tool and some data:
@@ -382,6 +385,68 @@ import { getDisplayName } from "@modelcontextprotocol/sdk/shared/metadataUtils.j
 const displayName = getDisplayName(tool);
 ```
 
+### Sampling
+
+MCP servers can request LLM completions from connected clients that support sampling.
+
+```typescript
+import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import { z } from "zod";
+
+const mcpServer = new McpServer({
+  name: "tools-with-sample-server",
+  version: "1.0.0",
+});
+
+// Tool that uses LLM sampling to summarize any text
+mcpServer.registerTool(
+  "summarize",
+  {
+    description: "Summarize any text using an LLM",
+    inputSchema: {
+      text: z.string().describe("Text to summarize"),
+    },
+  },
+  async ({ text }) => {
+    // Call the LLM through MCP sampling
+    const response = await mcpServer.server.createMessage({
+      messages: [
+        {
+          role: "user",
+          content: {
+            type: "text",
+            text: `Please summarize the following text concisely:\n\n${text}`,
+          },
+        },
+      ],
+      maxTokens: 500,
+    });
+
+    return {
+      content: [
+        {
+          type: "text",
+          text: response.content.type === "text" ? response.content.text : "Unable to generate summary",
+        },
+      ],
+    };
+  }
+);
+
+async function main() {
+  const transport = new StdioServerTransport();
+  await mcpServer.connect(transport);
+  console.log("MCP server is running...");
+}
+
+main().catch((error) => {
+  console.error("Server error:", error);
+  process.exit(1);
+});
+```
+
+
 ## Running Your Server
 
 MCP servers in TypeScript need to be connected to a transport to communicate with clients. How you start the server depends on the choice of transport:
@@ -588,8 +653,17 @@ app.delete('/mcp', async (req: Request, res: Response) => {
 
 // Start the server
 const PORT = 3000;
-app.listen(PORT, () => {
-  console.log(`MCP Stateless Streamable HTTP Server listening on port ${PORT}`);
+setupServer().then(() => {
+  app.listen(PORT, (error) => {
+    if (error) {
+      console.error('Failed to start server:', error);
+      process.exit(1);
+    }
+    console.log(`MCP Stateless Streamable HTTP Server listening on port ${PORT}`);
+  });
+}).catch(error => {
+  console.error('Failed to set up the server:', error);
+  process.exit(1);
 });
 
 ```

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@modelcontextprotocol/sdk",
-  "version": "1.13.2",
+  "version": "1.13.3",
   "description": "Model Context Protocol implementation for TypeScript",
   "license": "MIT",
   "author": "Anthropic, PBC (https://anthropic.com)",

package.json

@@ -403,6 +403,19 @@ describe("OAuth Authorization", () => {
       expect(mockFetch).toHaveBeenCalledTimes(2);
     });
 
+    it("returns undefined when both CORS requests fail in fetchWithCorsRetry", async () => {
+      // fetchWithCorsRetry tries with headers (fails with CORS), then retries without headers (also fails with CORS)
+      // simulating a 404 w/o headers set. We want this to return undefined, not throw TypeError
+      mockFetch.mockImplementation(() => {
+        // Both the initial request with headers and retry without headers fail with CORS TypeError
+        return Promise.reject(new TypeError("Failed to fetch"));
+      });
+
+      // This should return undefined (the desired behavior after the fix)
+      const metadata = await discoverOAuthMetadata("https://auth.example.com/path");
+      expect(metadata).toBeUndefined();
+    });
+
     it("returns undefined when discovery endpoint returns 404", async () => {
       mockFetch.mockResolvedValueOnce({
         ok: false,

src/client/auth.test.ts

@@ -292,25 +292,24 @@ export async function discoverOAuthProtectedResourceMetadata(
   return OAuthProtectedResourceMetadataSchema.parse(await response.json());
 }
 
-/**
- * Looks up RFC 8414 OAuth 2.0 Authorization Server Metadata.
- *
- * If the server returns a 404 for the well-known endpoint, this function will
- * return `undefined`. Any other errors will be thrown as exceptions.
- */
 /**
  * Helper function to handle fetch with CORS retry logic
  */
 async function fetchWithCorsRetry(
   url: URL,
-  headers: Record<string, string>,
-): Promise<Response> {
+  headers?: Record<string, string>,
+): Promise<Response | undefined> {
   try {
     return await fetch(url, { headers });
   } catch (error) {
-    // CORS errors come back as TypeError, retry without headers
     if (error instanceof TypeError) {
-      return await fetch(url);
+      if (headers) {
+        // CORS errors come back as TypeError, retry without headers
+        return fetchWithCorsRetry(url)
+      } else {
+        // We're getting CORS errors on retry too, return undefined
+        return undefined
+      }
     }
     throw error;
   }
@@ -334,7 +333,7 @@ function buildWellKnownPath(pathname: string): string {
 async function tryMetadataDiscovery(
   url: URL,
   protocolVersion: string,
-): Promise<Response> {
+): Promise<Response | undefined> {
   const headers = {
     "MCP-Protocol-Version": protocolVersion
   };
@@ -344,10 +343,16 @@ async function tryMetadataDiscovery(
 /**
  * Determines if fallback to root discovery should be attempted
  */
-function shouldAttemptFallback(response: Response, pathname: string): boolean {
-  return response.status === 404 && pathname !== '/';
+function shouldAttemptFallback(response: Response | undefined, pathname: string): boolean {
+  return !response || response.status === 404 && pathname !== '/';
 }
 
+/**
+ * Looks up RFC 8414 OAuth 2.0 Authorization Server Metadata.
+ *
+ * If the server returns a 404 for the well-known endpoint, this function will
+ * return `undefined`. Any other errors will be thrown as exceptions.
+ */
 export async function discoverOAuthMetadata(
   authorizationServerUrl: string | URL,
   opts?: { protocolVersion?: string },
@@ -362,18 +367,10 @@ export async function discoverOAuthMetadata(
 
   // If path-aware discovery fails with 404, try fallback to root discovery
   if (shouldAttemptFallback(response, issuer.pathname)) {
-    try {
-      const rootUrl = new URL("/.well-known/oauth-authorization-server", issuer);
-      response = await tryMetadataDiscovery(rootUrl, protocolVersion);
-
-      if (response.status === 404) {
-        return undefined;
-      }
-    } catch {
-      // If fallback fails, return undefined
-      return undefined;
-    }
-  } else if (response.status === 404) {
+    const rootUrl = new URL("/.well-known/oauth-authorization-server", issuer);
+    response = await tryMetadataDiscovery(rootUrl, protocolVersion);
+  }
+  if (!response || response.status === 404) {
     return undefined;
   }
 

src/client/auth.ts

@@ -74,6 +74,7 @@ test("should read messages", async () => {
   await client.close();
 });
 
+
 test("should properly set default environment variables in spawned process", async () => {
   await envAsyncLocalStorage.run({ env: {} }, async () => {
   const client = new StdioClientTransport(serverParameters);
@@ -128,4 +129,13 @@ test("should override default environment variables with custom ones", async ()
     }
     }
   });
+
+test("should return child process pid", async () => {
+  const client = new StdioClientTransport(serverParameters);
+
+  await client.start();
+  expect(client.pid).not.toBeNull();
+  await client.close();
+  expect(client.pid).toBeNull();
+
 });

src/client/stdio.test.ts

@@ -189,6 +189,15 @@ export class StdioClientTransport implements Transport {
     return this._process?.stderr ?? null;
   }
 
+  /**
+   * The child process pid spawned by this transport.
+   *
+   * This is only available after the transport has been started.
+   */
+  get pid(): number | null {
+    return this._process?.pid ?? null;
+  }
+
   private processReadBuffer() {
     while (true) {
       try {

src/client/stdio.ts

@@ -43,7 +43,14 @@ server.registerTool(
     void country;
     // Simulate weather API call
     const temp_c = Math.round((Math.random() * 35 - 5) * 10) / 10;
-    const conditions = ["sunny", "cloudy", "rainy", "stormy", "snowy"][Math.floor(Math.random() * 5)];
+    const conditionCandidates = [
+      "sunny",
+      "cloudy",
+      "rainy",
+      "stormy",
+      "snowy",
+    ] as const;
+    const conditions = conditionCandidates[Math.floor(Math.random() * conditionCandidates.length)];
 
     const structuredContent = {
       temperature: {
@@ -77,4 +84,4 @@ async function main() {
 main().catch((error) => {
   console.error("Server error:", error);
   process.exit(1);
-});
+});

src/examples/server/mcpServerOutputSchema.ts

@@ -0,0 +1,57 @@
+
+// Run with: npx tsx src/examples/server/toolWithSampleServer.ts
+
+import { McpServer } from "../../server/mcp.js";
+import { StdioServerTransport } from "../../server/stdio.js";
+import { z } from "zod";
+
+const mcpServer = new McpServer({
+  name: "tools-with-sample-server",
+  version: "1.0.0",
+});
+
+// Tool that uses LLM sampling to summarize any text
+mcpServer.registerTool(
+  "summarize",
+  {
+    description: "Summarize any text using an LLM",
+    inputSchema: {
+      text: z.string().describe("Text to summarize"),
+    },
+  },
+  async ({ text }) => {
+    // Call the LLM through MCP sampling
+    const response = await mcpServer.server.createMessage({
+      messages: [
+        {
+          role: "user",
+          content: {
+            type: "text",
+            text: `Please summarize the following text concisely:\n\n${text}`,
+          },
+        },
+      ],
+      maxTokens: 500,
+    });
+
+    return {
+      content: [
+        {
+          type: "text",
+          text: response.content.type === "text" ? response.content.text : "Unable to generate summary",
+        },
+      ],
+    };
+  }
+);
+
+async function main() {
+  const transport = new StdioServerTransport();
+  await mcpServer.connect(transport);
+  console.log("MCP server is running...");
+}
+
+main().catch((error) => {
+  console.error("Server error:", error);
+  process.exit(1);
+});

src/examples/server/toolWithSampleServer.ts

@@ -267,6 +267,7 @@ describe("tool()", () => {
     expect(result.tools[0].name).toBe("test");
     expect(result.tools[0].inputSchema).toEqual({
       type: "object",
+      properties: {},
     });
 
     // Adding the tool before the connection was established means no notification was sent
@@ -1311,7 +1312,7 @@ describe("tool()", () => {
           resultType: "structured",
           // Missing required 'timestamp' field
           someExtraField: "unexpected" // Extra field not in schema
-        },
+        } as unknown as { processedInput: string; resultType: string; timestamp: string }, // Type assertion to bypass TypeScript validation for testing purposes
       })
     );