mcp-express-example

clerk/mcp-express-example

3.3

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This is a demonstration of a simple MCP server using Express and Clerk, designed to showcase a basic implementation of a streamable HTTP handler.

Express & Clerk MCP Server Demo

The simplest, most bare bones implementation of an MCP server, using express. At the moment, it only exposes a streamable http handler. It could be adapted to handle SSE as well if necessary though. The purpose of this example is to serve as a proof of concept!

Getting started

  • Run npm i to install dependencies
  • Run cp .env.sample .env and copy your Clerk API keys from your dashboard into the .env file
  • Run npm start to start the server
  • You should be able to connect to it now from any client that supports tha latest version of the MCP spec. A cursor configuration is provided as a test.

HTTPS Setup (Optional)

By default, the server runs on HTTP only. To enable HTTPS for development (useful for testing with some clients), you'll need to generate locally trusted certificates:

  1. Install mkcert (if not already installed):

    # macOS
brew install mkcert

# Windows (using Chocolatey)
choco install mkcert

# Linux
# See https://github.com/FiloSottile/mkcert#installation

  2. Setup local certificate authority:

    mkcert -install

  3. Generate certificates:

    mkcert localhost 127.0.0.1 ::1
mkdir -p cert
mv localhost+2*.pem cert/

  4. Restart the server - it will automatically detect the certificates and start both HTTP (port 3000) and HTTPS (port 3001) servers.

The certificates are gitignored, so each developer needs to generate their own locally trusted certificates.