Calculator MCP Server

A simple MCP server built with FastMCP that exposes an addition tool and a server info resource.

Prerequisites

• Python 3.10+
• uv package manager

Setup

Clone the repo and install dependencies:

uv sync

Running the Server

Option 1 — HTTP Server (production / remote)

Starts the server on http://0.0.0.0:8000:

uv run python main.py

The MCP endpoint will be available at:

http://localhost:8000/mcp

Option 2 — Dev Mode with MCP Inspector (recommended for development)

Launches the server with the interactive MCP Inspector UI for testing tools and resources:

uv run fastmcp dev inspector main.py:mcp

Then open the Inspector UI in your browser:

http://localhost:6274

Tools

add

Adds two numbers and returns their sum.

Example: add(3, 7) → 10.0

Resources

info://server

Returns a description of this MCP server, its tools, and resources.

Connecting to a Client

To connect a client (e.g. Claude Desktop, Cursor) to the running HTTP server, use:

• Transport: Streamable HTTP
• URL: http://localhost:8000/mcp

For Claude Desktop, add the following to your claude_desktop_config.json:

{
  "mcpServers": {
    "calculator": {
      "command": "uv",
      "args": ["run", "python", "/absolute/path/to/main.py"]
    }
  }
}