MCP Inspector is a browser-based debugging tool for testing MCP servers without first building a complete MCP client. It connects to a server, displays exposed capabilities, and lets you invoke tools. section 7.3.4 section 7.4.2
Use the inspector to verify an MCP server incrementally:
- Start it with npx and open the browser URL, including MCP_PROXY_AUTH_TOKEN when the console provides one. section 7.3.4
- For a packaged Java server, enter java as the command and -jar plus the executable JAR path as arguments. section 7.3.4
- Set SPRING_DOCKER_COMPOSE_FILE when the server depends on a compose.yaml file outside its JAR. section 7.3.4
- Select SSE and the server endpoint, connect, list tools, supply parameters, and run a selected tool. section 7.4.2
Testing an HTTP+SSE server
After starting the server on port 3001, open http://localhost:5173, choose SSE with http://localhost:3001/sse, connect, and invoke findGamesForPlayerCount with 5 as its parameter. section 7.4.2
$ npx @modelcontextprotocol/inspector
The startup command provides the shortest path to launching the inspector before connecting it to a local MCP server. section 7.3.4
