MCP Inspectorで調査する

Editing config and restarting is slow for testing. The MCP Inspector gives you a visual tool to poke at your server directly. 🔍

The Inspector is an official web app that acts as a client. It connects to your server and lets you browse and call everything it exposes.

You don’t install anything permanently. Run it on demand with npx, and it opens a local web UI in your browser.

If you use the Python SDK, the mcp dev command launches the very same Inspector wired to your server in one step.

The Inspector spawns your script just like a host would, talking over stdio. So you test the exact path a real client uses.

Open the Tools tab to list every tool your server advertises, complete with its name, description, and expected arguments.

Pick a tool, fill in its fields in the form, and hit run. You see the exact result the server returns, with no model in the loop.

The Resources tab shows everything your server can serve. Click one to read its contents and confirm the URI resolves correctly.

Under Prompts you can fill in arguments and preview the exact messages your template produces before any user ever triggers it.

A built-in log pane shows raw JSON-RPC traffic in both directions. It is the fastest way to see what your server truly sent.

Changed your code? Hit reconnect in the Inspector to restart the server and reload its tools, far faster than restarting a full host.

Why is the MCP Inspector handy when developing a server?

You used the Inspector to list tools, call them by hand, browse resources and prompts, and watch the wire. Now let’s tackle servers that won’t start. ✅