概要
What is MCP Inspector?
MCP Inspector is a developer tool for testing and debugging MCP servers. It consists of a React-based web UI (MCPI) that connects to MCP servers via a Node.js proxy (MCPP) supporting stdio, SSE, and streamable-http transports. It is intended for developers building or debugging MCP server implementations.
How to use MCP Inspector?
Run npx @modelcontextprotocol/inspector to start the UI at http://localhost:6274. To inspect a server from its repository, use npx @modelcontextprotocol/inspector node build/index.js with optional arguments and -e flags for environment variables. A Docker image is also available. Ports can be customized via CLIENT_PORT and SERVER_PORT environment variables.
Key features of MCP Inspector
- Interactive web UI for testing MCP servers
- Supports stdio, SSE, and streamable-http transports
- Bearer token authentication with session tokens
- Export server launch configurations as mcp.json
- Real-time adjustable timeout settings
- Persists configuration across sessions
Use cases of MCP Inspector
- Debugging MCP server implementations during development
- Testing server tools and resources interactively
- Validating server configuration for different transport protocols
- Exporting server configurations for use in clients like Cursor or Claude Code
FAQ from MCP Inspector
Is MCP Inspector a network proxy for intercepting traffic?
No, it functions as both an MCP client and an HTTP server, enabling browser-based interaction with MCP servers via different transport protocols.
What are the runtime requirements?
Node.js version ^22.7.5 is required.
How does authentication work?
The proxy requires a session token (randomly generated) sent as a Bearer token in the Authorization header. The token is shown in the console and can be pre-filled in the UI.
Can I expose the inspector to other devices?
By default it binds only to localhost. Binding to all interfaces (HOST=0.0.0.0) is possible but dangerous because the proxy can spawn local processes.
What transport protocols does the inspector support?
It supports stdio, SSE (Server-Sent Events), and streamable-http transports.
