Cloudflare Google OAuth MCP Server

Model Context Protocol (MCP) Server + Google OAuth

This is a Model Context Protocol (MCP) server that supports remote MCP connections, with Google OAuth built-in.

You can deploy it to your own Cloudflare account, and after you create your own Google Cloud OAuth client app, you'll have a fully functional remote MCP server that you can build off. Users will be able to connect to your MCP server by signing in with their Google account.

You can use this as a reference example for how to integrate other OAuth providers with an MCP server deployed to Cloudflare, using the `workers-oauth-provider` library.

The MCP server (powered by Cloudflare Workers):

• Acts as OAuth Server to your MCP clients
• Acts as OAuth Client to your real OAuth server (in this case, Google)

Getting Started

Clone the repo & install dependencies: npm install

For Production

Create a new Google Cloud OAuth App:

• For the Homepage URL, specify https://mcp-google-oauth.<your-subdomain>.workers.dev
• For the Authorization callback URL, specify https://mcp-google-oauth.<your-subdomain>.workers.dev/callback
• Note your Client ID and generate a Client secret.
• Set secrets via Wrangler

wrangler secret put GOOGLE_CLIENT_ID
wrangler secret put GOOGLE_CLIENT_SECRET
wrangler secret put COOKIE_ENCRYPTION_KEY # add any random string here e.g. openssl rand -hex 32
wrangler secret put HOSTED_DOMAIN # optional: use this when restrict google account domain
wrangler secret put ALLOWED_API_KEYS # comma-separated list of API keys (e.g., key1,key2,key3)

Note: The server now requires API Key authentication for MCP endpoints. See API_KEY_SETUP.md for detailed setup instructions.

Set up a KV namespace

• Create the KV namespace: wrangler kv:namespace create "OAUTH_KV"
• Update the Wrangler file with the KV ID

Deploy & Test

Deploy the MCP server to make it available on your workers.dev domain wrangler deploy

Test the remote server using Inspector:

npx @modelcontextprotocol/inspector@latest

Enter https://mcp-google-oauth.<your-subdomain>.workers.dev/mcp and hit connect. Once you go through the authentication flow, you'll see the Tools working:

You now have a remote MCP server deployed!

Access Control

This MCP server uses Google Cloud OAuth for authentication. All authenticated Google users can access basic tools like "add". When you restrict users with hosted domain, set HOSTED_DOMAIN env.

Access the remote MCP server from Claude Desktop

Open Claude Desktop and navigate to Settings -> Developer -> Edit Config. This opens the configuration file that controls which MCP servers Claude can access.

Replace the content with the following configuration. Once you restart Claude Desktop, a browser window will open showing your OAuth login page. Complete the authentication flow to grant Claude access to your MCP server. After you grant access, the tools will become available for you to use.

{
  "mcpServers": {
    "math": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://mcp-google-oauth.<your-subdomain>.workers.dev/mcp"
      ]
    }
  }
}

Once the Tools (under 🔨) show up in the interface, you can ask Claude to use them. For example: "Could you use the math tool to add 23 and 19?". Claude should invoke the tool and show the result generated by the MCP server.

For Local Development

If you'd like to iterate and test your MCP server, you can do so in local development. This will require you to create another OAuth App on Google Cloud:

• For the Homepage URL, specify http://localhost:8788
• For the Authorization callback URL, specify http://localhost:8788/callback
• Note your Client ID and generate a Client secret.
• Create a .dev.vars file in your project root with:

GOOGLE_CLIENT_ID=your_development_google_cloud_oauth_client_id
GOOGLE_CLIENT_SECRET=your_development_google_cloud_oauth_client_secret
COOKIE_ENCRYPTION_KEY=any_random_string_here
ALLOWED_API_KEYS=dev-key-1,dev-key-2

Develop & Test

Run the server locally to make it available at http://localhost:8788 wrangler dev

To test the local server, enter http://localhost:8788/mcp into Inspector and hit connect. Once you follow the prompts, you'll be able to "List Tools".

Using Claude and other MCP Clients

When using Claude to connect to your remote MCP server, you may see some error messages. This is because Claude Desktop doesn't yet support remote MCP servers, so it sometimes gets confused. To verify whether the MCP server is connected, hover ov