calculator_server.py

from fastmcp import FastMCP
from fastmcp.exceptions import ToolError
import logging
import os

# Set up logging to see what's happening
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# 1. Create a FastMCP server instance
mcp = FastMCP(name="Calculator 🧮")

# 2. Define tools using the @mcp.tool decorator
@mcp.tool
def add(a: float, b: float) -> float:
    """Adds two numbers together."""
    logger.info(f"Adding {a} + {b}")
    return a + b

@mcp.tool
def multiply(a: float, b: float) -> float:
    """Multiplies two numbers."""
    logger.info(f"Multiplying {a} * {b}")
    return a * b

@mcp.tool
def divide(a: float, b: float) -> float:
    """
    Divides the first number by the second.
    Raises an error if the second number is zero.
    """
    logger.info(f"Dividing {a} / {b}")
    if b == 0:
        raise ToolError("Division by zero is not allowed.")
    return a / b

# 3. Add a main block to run the server
if __name__ == "__main__":
    port = int(os.environ.get("PORT", 7860))
    logger.info(f"Starting FastMCP server on host 0.0.0.0 port {port}")
    
    try:
        # FastMCP only supports streamable-http transport
        mcp.run(transport="streamable-http", host="0.0.0.0",
            port=7860,
            path="/mcp")
    except Exception as e:
        logger.error(f"Failed to start server: {e}")
        raise