Remote MCP Server On Cloudflare J4s

🚀 Running a Remote MCP Server on Cloudflare

Let's build a remote MCP server running on Cloudflare Workers and integrate OAuth login functionality!

🚀 Quick Start

📦 Installation

# Clone the repository
git clone git@github.com:cloudflare/ai.git

# Install dependencies
cd ai
npm install

# Run locally
npx nx dev remote-mcp-server

You should be able to open a browser window at http://localhost:8787/.

💻 Usage Examples

Connect the MCP Inspector to Your Server

To explore the new MCP API, you can use the MCP Inspector.

• Start it with npx @modelcontextprotocol/inspector.
• In the inspector, switch the transport type to SSE and enter http://localhost:8787/sse as the URL of the MCP server, then click "Connect".
• You'll enter a (simulated) user/password login screen. Enter any email and password to log in.
• You should be redirected back to the MCP Inspector and can list and call any defined tools!

Connect Claude Desktop to Your Local MCP Server

The MCP Inspector is great, but what we really want to do is connect it to Claude! Follow Anthropic's Quick Start Guide, go to Settings > Developer > Edit Configuration in Claude Desktop to find your configuration file.

Open the file with a text editor and replace it with the following configuration:

{
  "mcpServers": {
    "math": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "http://localhost:8787/sse"
      ]
    }
  }
}

This will run a local proxy that allows Claude to communicate with your MCP server over HTTP.

When you open Claude, a browser window should open and allow you to log in. You should see available tools in the bottom right corner. As prompted, Claude should be able to call the tools.

Connect Claude Desktop to Your Remote MCP Server

Update the Claude configuration file to point to your workers.dev URL (e.g., https://worker-name.account-name.workers.dev/sse), then restart Claude.

{
  "mcpServers": {
    "math": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://worker-name.account-name.workers.dev/sse"
      ]
    }
  }
}

🚀 Deployment

Deploy to Cloudflare

1. npx wrangler kv namespace create OAUTH_KV
2. Follow the instructions to add the KV namespace ID to wrangler.jsonc
3. npm run deploy

Call Your Newly Deployed Remote MCP Server from a Remote MCP Client

Just like in "Local Development", run the MCP Inspector: npx @modelcontextprotocol/inspector@latest

Then, in the inspector, enter your Cloudflare Worker's workers.dev URL (e.g., worker-name.account-name.workers.dev/sse) as the URL of the MCP server and click "Connect".

You've now connected the MCP server from a remote MCP client.

🔧 Debugging

If you encounter any issues, restarting Claude or directly connecting to your MCP server via the command line may help.

npx mcp-remote http://localhost:8787/sse

In rare cases, clearing the files in the ~/.mcp-auth directory may be helpful.

rm -rf ~/.mcp-auth