MCP Inspector

The MCP Inspector is a developer tool designed for testing and debugging MCP (Model Context Protocol) servers. It includes a client UI and an MCP proxy server.

Running the Inspector

To inspect an MCP server, use npx @modelcontextprotocol/inspector followed by the server's entry point (e.g., node build/index.js). Arguments and environment variables can be passed to the server. Use -e KEY=value for environment variables and -- to separate inspector flags from server arguments. The client UI runs on port 5173 (default), and the proxy server runs on port 3000 (default), both customizable via CLIENT_PORT and SERVER_PORT environment variables. Refer to the MCP documentation for usage details and debugging guides.

The inspector supports bearer token authentication for SSE connections, which can be entered in the UI.

Security Note: The proxy server should not be exposed to untrusted networks due to its ability to spawn local processes.

For inspector development: npm run dev (or npm run dev:windows on Windows) for development mode, and npm run build followed by npm start for production mode.

License

Licensed under the MIT License.