MCP Inspector

The MCP inspector is a developer tool for testing and debugging MCP servers.

Running the Inspector

From an MCP server repository

To inspect an MCP server implementation, there's no need to clone this repo. Instead, use npx. For example, if your server is built at build/index.js:

npx @modelcontextprotocol/inspector build/index.js

You can also pass arguments along which will get passed as arguments to your MCP server:

npx @modelcontextprotocol/inspector build/index.js arg1 arg2 ...

The inspector runs both a client UI (default port 5173) and an MCP proxy server (default port 3000). Open the client UI in your browser to use the inspector. You can customize the ports if needed:

CLIENT_PORT=8080 SERVER_PORT=9000 npx @modelcontextprotocol/inspector build/index.js

For more details on ways to use the inspector, see the Inspector section of the MCP docs site.

From this repository

If you're working on the inspector itself:

Development mode:

npm run dev

Production mode:

npm run build
npm start

License

This project is licensed under the MIT License—see the LICENSE file for details.