Building MCP Servers on Cloudflare Skill

Building MCP Servers on Cloudflare

Retrieval Sources

| Source | URL | |--------|-----| | MCP docs | https://developers.cloudflare.com/agents/mcp/ | | MCP spec | https://modelcontextprotocol.io/ | | Workers docs | https://developers.cloudflare.com/workers/ |

When to Use

User wants to build a remote MCP server
User needs to expose tools via MCP
User asks about MCP authentication or OAuth
User wants to deploy MCP to Cloudflare Workers

Quick Start - Public Server (No Auth)

npm create cloudflare@latest -- my-mcp-server \
  --template=cloudflare/ai/demos/remote-mcp-authless
cd my-mcp-server
npm start

Server runs at http://localhost:8788/mcp

Quick Start - Authenticated Server (OAuth)

npm create cloudflare@latest -- my-mcp-server \
  --template=cloudflare/ai/demos/remote-mcp-github-oauth
cd my-mcp-server

Define Tools

import { McpAgent } from "agents/mcp";
import { z } from "zod";

export class MyMCP extends McpAgent {
  server = new Server({ name: "my-mcp", version: "1.0.0" });

  async init() {
    this.server.tool(
      "add",
      { a: z.number(), b: z.number() },
      async ({ a, b }) => ({
        content: [{ type: "text", text: String(a + b) }],
      })
    );

    this.server.tool(
      "get_weather",
      { city: z.string() },
      async ({ city }) => {
        const response = await fetch(`https://api.weather.com/${city}`);
        const data = await response.json();
        return {
          content: [{ type: "text", text: JSON.stringify(data) }],
        };
      }
    );
  }
}

Entry Point

import { MyMCP } from "./mcp";

export default {
  fetch(request: Request, env: Env, ctx: ExecutionContext) {
    const url = new URL(request.url);
    if (url.pathname === "/mcp") {
      return MyMCP.serveSSE("/mcp").fetch(request, env, ctx);
    }
    return new Response("MCP Server", { status: 200 });
  },
};

export { MyMCP };

Deploy

npx wrangler deploy

Server accessible at https://[worker-name].[account].workers.dev/mcp

Connect Clients

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["mcp-remote", "https://my-mcp.workers.dev/mcp"]
    }
  }
}

Tool Return Types

return { content: [{ type: "text", text: "result" }] };
return {
  content: [
    { type: "text", text: "Here's the data:" },
    { type: "text", text: JSON.stringify(data, null, 2) },
  ],
};

Input Validation with Zod

this.server.tool(
  "create_user",
  {
    email: z.string().email(),
    name: z.string().min(1).max(100),
    role: z.enum(["admin", "user", "guest"]),
    age: z.number().int().min(0).optional(),
  },
  async (params) => { }
);

Accessing Bindings

export class MyMCP extends McpAgent<Env> {
  async init() {
    this.server.tool("query_db", { sql: z.string() }, async ({ sql }) => {
      const result = await this.env.DB.prepare(sql).all();
      return { content: [{ type: "text", text: JSON.stringify(result) }] };
    });
  }
}

Wrangler Configuration

name = "my-mcp-server"
main = "src/index.ts"
compatibility_date = "2024-12-01"

[durable_objects]
bindings = [{ name = "MCP", class_name = "MyMCP" }]

[[migrations]]
tag = "v1"
new_classes = ["MyMCP"]

OAuth Providers Supported

GitHub, Google, Auth0, Stytch, WorkOS, and any OAuth 2.0 compliant provider.

Keywords

Cloudflare, MCP, Model Context Protocol, remote MCP, OAuth, tools, server, Workers

Agent Skills: Building MCP Servers on Cloudflare

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