mcp-worker-authenticated

Authenticated MCP Server

An MCP server protected by OAuth 2.1, using @cloudflare/workers-oauth-provider. Clients must complete the OAuth flow before calling tools — the auth context is then available inside tool handlers.

What it demonstrates

• OAuth 2.1 with MCP — dynamic client registration, authorization code flow, and token exchange
• OAuthProvider — wrapping createMcpHandler with @cloudflare/workers-oauth-provider
• getMcpAuthContext() — accessing the authenticated user's identity inside tool handlers
• Custom authorization UI — a Hono-based approval page for the OAuth flow

Running

First, create a KV namespace for OAuth state:

npx wrangler kv namespace create OAUTH_KV

Update the kv_namespaces binding in wrangler.jsonc with the returned ID, then:

npm install
npm run dev

Open the browser to see the server info page. To test the tools, use the MCP Inspector — it will handle the OAuth flow automatically.

How it works

The OAuthProvider wraps the entire Worker. It intercepts OAuth endpoints (/authorize, /oauth/token, /oauth/register) and validates Bearer tokens on the API route (/mcp).

import { OAuthProvider } from "@cloudflare/workers-oauth-provider";
import { createMcpHandler, getMcpAuthContext } from "agents/mcp";

const apiHandler = {
  async fetch(request, env, ctx) {
    const server = createServer();
    return createMcpHandler(server)(request, env, ctx);
  }
};

export default new OAuthProvider({
  authorizeEndpoint: "/authorize",
  tokenEndpoint: "/oauth/token",
  clientRegistrationEndpoint: "/oauth/register",
  apiRoute: "/mcp",
  apiHandler,
  defaultHandler: { fetch: (req, env, ctx) => AuthHandler.fetch(req, env, ctx) }
});

Inside tool handlers, access the authenticated user:

server.registerTool("whoami", { description: "Who am I?" }, async () => {
  const auth = getMcpAuthContext();
  return {
    content: [{ type: "text", text: JSON.stringify(auth?.props) }]
  };
});

Related examples

• mcp-worker — same stateless pattern without authentication
• mcp-client — connecting to authenticated MCP servers as a client (handles OAuth automatically)