The MCP inspector is a developer tool for testing and debugging MCP servers.
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.jsYou 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.jsYou can import environment variables from a .env file using the import button in the UI. The .env file should follow the standard format:
KEY1=value1
KEY2=value2
For more details on ways to use the inspector, see the Inspector section of the MCP docs site. For help with debugging, see the Debugging guide.
If you're working on the inspector itself:
Development mode:
npm run devProduction mode:
npm run build
npm startThis project is licensed under the MIT License—see the LICENSE file for details.