How to use MCP Inspector

MCP Insepctor can be used to test multiple types of transport, http, sse or stdio. We will be using the http-streaming for this tutorial. The official mcp sdk for python uses fastmcp 1.0 as of this writing, but we will be using 2.0

Lets create and run a simple mcp server

For this we will use FastMCP 2.0, Here is a quick example

lets first create a project

uv init greeting
cd greeting
uv add fastmcp

Now open this folder in vscode or your editor and modify main.py

from fastmcp import FastMCP

mcp = FastMCP("My MCP Server")

@mcp.tool
def greet(name: str) -> str:
    return f"Hello, {name}!"

To run this

uv run fastmcp run main.py --transport http

This will run your server with http streaming

Running the inspector

You need nodejs installed. You can download nodejs from

https://nodejs.org

npx @modelcontextprotocol/inspector 

When you run the inspector, you will see a url printed on the screen which includes the proxy token.

the output will look like below, copy the url

npx @modelcontextprotocol/inspector
Starting MCP inspector...
⚙️ Proxy server listening on 127.0.0.1:6277
🔑 Session token: a85ec289a6242bf47e7fb4822207138908c2b478c1a329f1b36432cdbf3b0385
Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth

🔗 Open inspector with token pre-filled:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=a85ec289a6242bf47e7fb4822207138908c2b478c1a329f1b36432cdbf3b0385

Change the url to

http://localhost:8000/mcp and click on connect

Now click on Tools -> List Tools

You should see your greet tool

In order to test it, click on it and you should see the result as below