MCP Inspector

MCP Inspector is an open-source developer tool for testing and debugging Model Context Protocol (MCP) servers. It consists of a React-based web UI (MCP Inspector Client) and a Node.js proxy server (MCP Proxy) that acts as a protocol bridge, enabling browser-based interaction with MCP servers over stdio, SSE, and streamable-HTTP transports. Developers can launch it instantly via npx @modelcontextprotocol/inspector or run it in a Docker container, with no repository cloning required. It also ships a CLI mode for scripting, automation, and CI/CD integration.

• React Web UI — Interactive interface for visually exploring tools, resources, and prompts on any MCP server; accessible at http://localhost:6274 after launch.
• MCP Proxy Bridge — Node.js server that acts as both an MCP client and HTTP server, connecting the browser UI to MCP servers using stdio, SSE, or streamable-HTTP transports.
• CLI Mode — Run npx @modelcontextprotocol/inspector --cli node build/index.js to interact with MCP servers programmatically for scripting, batch processing, and CI/CD pipelines.
• Multiple Transport Support — Supports stdio, SSE (Server-Sent Events), and streamable-HTTP transport types, configurable via command-line flags or JSON config files.
• Config File Support — Define multiple MCP server configurations in a mcp.json file and switch between them using --config and --server flags.
• Servers File Export — Export server launch configurations (Server Entry or full Servers File) to clipboard for use in clients like Cursor or Claude Code.
• Bearer Token Authentication — Supports bearer token auth for SSE connections; the proxy generates a random session token on startup and auto-opens the browser with it pre-filled.
• Security Hardening — Binds to localhost by default, validates Origin headers to prevent DNS rebinding attacks, and warns against disabling authentication.
• Configurable Timeouts — Adjust client-side request timeouts, progress-notification resets, and max total timeouts via the UI or environment variables.
• Docker Support — Run the inspector in an isolated Docker container with a single docker run command, mapping ports 6274 and 6277.