FastMCP Demo Server

A beginner-friendly Model Context Protocol (MCP) server built with FastMCP. This project demonstrates how to create custom MCP tools and connect them to AI clients such as Claude Desktop.

🚀 Features

This server currently provides two simple MCP tools:

• add — Adds two numbers

• multiply — Multiplies two numbers

The project is designed as a simple starting point for learning how MCP servers work.

Related MCP server: Calculator MCP Server

🧠 How It Works

The basic architecture is:

User
  ↓
AI Client (Claude Desktop)
  ↓
MCP Protocol
  ↓
FastMCP Server
  ↓
Custom Tools
  ↓
Python Functions

For example, when Claude needs to calculate 10 + 20, it can call the add MCP tool:

Claude
  ↓
add(10, 20)
  ↓
FastMCP Server
  ↓
Python function
  ↓
30

📁 Project Structure

fastmcp-demo-server/
│
├── main.py
├── README.md
├── LICENSE
├── pyproject.toml
├── uv.lock
├── .python-version
└── .gitignore

🛠️ Tools

1. add

Adds two numbers.

add(a, b)

Example:

add(10, 20)
→ 30

2. multiply

Multiplies two numbers.

multiply(a, b)

Example:

multiply(10, 20)
→ 200

⚙️ Requirements

• Python

• uv

• FastMCP

• An MCP-compatible client such as Claude Desktop

📦 Installation

Clone the repository:

git clone https://github.com/safayet9009/fastmcp-demo-server.git

Go to the project directory:

cd fastmcp-demo-server

Install the project dependencies:

uv sync

▶️ Run the Server

Run the MCP server with:

uv run fastmcp run main.py:mcp

The server uses stdio transport, so it can communicate directly with MCP clients such as Claude Desktop.

🔍 Test with FastMCP Inspector

You can also inspect and test the server using FastMCP's development tools:

uv run fastmcp dev inspector main.py:mcp

This allows you to explore the available MCP tools and test them interactively.

🤖 Connect with Claude Desktop

Add the following configuration to your Claude Desktop MCP configuration:

{
  "mcpServers": {
    "Demo Server": {
      "command": "/home/shafayet/.local/bin/uv",
      "args": [
        "run",
        "--directory",
        "/home/shafayet/Desktop/fastmcp-demo-server",
        "fastmcp",
        "run",
        "main.py:mcp"
      ],
      "env": {},
      "transport": "stdio"
    }
  }
}

Note: Update the paths according to your own system.

After adding the configuration, restart Claude Desktop.

Claude should then be able to discover the available tools:

add
multiply

You can test it by asking Claude:

Use the add tool to calculate 25 + 75.

or:

Use the multiply tool to calculate 12 × 8.

🎯 Learning Goals

This project helps demonstrate:

• What an MCP server is

• How FastMCP works

• How to create MCP tools

• How MCP clients discover and call tools

• How Python functions can become MCP tools

• How to connect a custom MCP server with Claude Desktop

• How stdio transport works

🔮 Future Improvements

Possible future additions include:

• Weather tool

• Calculator tool

• Web search tool

• Database tools

• File management tools

• API integration

• Custom AI-powered tools

• Resources and prompts

• Authentication

• More advanced MCP workflows

📄 License

This project is licensed under the MIT License. See the LICENSE file for details.

👨‍💻 Author

Safayet Hossain

GitHub: @safayet9009

⭐ If you find this project useful for learning MCP, consider giving it a star!