Connect It to an AI Client

Point Cursor or Claude Desktop at your stdio server and actually invoke a tool from the assistant.

A server that only runs under mcp dev is a lab. This lesson wires the host you already use so the model can call ping or greet in a real chat.

What the host needs

A command it can exec (the venv’s python, not a global one that lacks mcp).
Args — usually the path to server.py.
A working directory if the script reads relative files.

Cursor

Project or user MCP config is JSON. A typical project file is .cursor/mcp.json:

{
  "mcpServers": {
    "hello": {
      "command": "C:\\\\path\\\\to\\\\hello-mcp\\\\.venv\\\\Scripts\\\\python.exe",
      "args": ["C:\\\\path\\\\to\\\\hello-mcp\\\\server.py"]
    }
  }
}

On macOS or Linux use the venv’s bin/python and normal slashes. Restart Cursor (or reload MCP) after you save. The server name hello is what you will see in the tools list.

Claude Desktop

Claude Desktop uses a similar mcpServers map in its config JSON (location depends on OS). Same idea: absolute command and args. Quit the app fully after edits — a tray restart often keeps the old process.

Use a tool on purpose

Start a new chat and ask a question that requires the tool (“Call ping on my hello server”).
Approve the tool call if the host asks.
Confirm the reply includes pong or your greeting, not a hallucination.

Next: keep API keys out of tool text.