Calculator MCP Server

A simple calculator MCP (Model Context Protocol) server that exposes arithmetic operations as tools for AI assistants like Claude.

What is MCP?

Model Context Protocol (MCP) is an open protocol that enables AI assistants to interact with external tools and data sources. This server demonstrates how to build MCP tools using Python.

Features

Tool	Description	Example
add	Add two numbers	add(5, 3) → 8
subtract	Subtract numbers	subtract(10, 4) → 6
multiply	Multiply numbers	multiply(6, 7) → 42
divide	Divide with zero-check	divide(15, 3) → 5.0
power	Exponentiation	power(2, 3) → 8.0
modulo	Remainder operation	modulo(17, 5) → 2
square_root	Square root	square_root(16) → 4.0
absolute	Absolute value	absolute(-5) → 5
percentage	Calculate percentage	percentage(200, 15) → 30.0

Installation

Prerequisites

• Python 3.10 or higher
• pip package manager

Install from source

git clone https://github.com/Sathiya-Moorthi/MCP.git
cd calculator-mcp
pip install -e .

Install dependencies only

pip install mcp

Usage

With Claude Desktop

Add to your Claude Desktop configuration file:

Windows: %APPDATA%\Claude\claude_desktop_config.json macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "calculator": {
      "command": "python",
      "args": ["/path/to/calculator-mcp/calculator_server.py"]
    }
  }
}

Restart Claude Desktop, then ask Claude to perform calculations!

With Cursor IDE

Add to your Cursor MCP configuration (~/.cursor/mcp.json):

{
  "mcpServers": {
    "calculator": {
      "command": "python",
      "args": ["/path/to/calculator-mcp/calculator_server.py"]
    }
  }
}

Standalone Testing

python calculator_server.py

The server communicates via stdio (standard input/output) using the MCP protocol.

Development

Setup development environment

# Clone the repository
git clone https://github.com/Sathiya-Moorthi/MCP.git
cd calculator-mcp

# Create virtual environment
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install dependencies
pip install -e ".[dev]"

Run tests

pytest

Project Structure

calculator-mcp/
├── calculator_server.py    # Main MCP server implementation
├── pyproject.toml          # Project configuration
├── tests/
│   └── test_calculator.py  # Unit tests
├── .github/
│   └── workflows/
│       └── ci.yml          # GitHub Actions CI
├── README.md
├── LICENSE
└── .gitignore

How It Works

This server uses FastMCP, a high-level API from the official MCP Python SDK:

from mcp.server.fastmcp import FastMCP

mcp = FastMCP(name="calculator")

@mcp.tool()
def add(a: float, b: float) -> float:
    """Add two numbers together."""
    return a + b

if __name__ == "__main__":
    mcp.run()

Key concepts:

• @mcp.tool() decorator - Registers functions as MCP tools
• Type hints - Define parameter types for validation
• Docstrings - Become tool descriptions visible to AI
• mcp.run() - Starts the server with stdio transport

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Acknowledgments

• Anthropic for the MCP protocol
• MCP Python SDK