What is MCP Inspector?

MCP Inspector is the reference debugging tool maintained by the Model Context Protocol project. It is a browser-based UI you typically launch with npx that connects to any MCP server, local over stdio or remote over Streamable HTTP, and gives you a hands-on view of what the server actually exposes. You can see the capabilities negotiated during initialization, browse the list of tools with their input schemas, read available resources, try out prompts, and crucially invoke tools by hand with arbitrary arguments to confirm they behave as intended. It surfaces the underlying JSON-RPC traffic too, so when something misbehaves you can see the exact request and response rather than guessing. For anyone building or integrating a server, Inspector is usually the first stop: stand up the server, point Inspector at it, and verify the tool surface and auth flow before wiring it into a real host. It shortens the debug loop considerably compared with testing through a full chat application where errors are easy to misattribute.