How to use Claude with custom MCP tools

pip install anthropic mcp

import os
from anthropic import Anthropic
from mcp.server import Server, Tool
from mcp.server.stdio import stdio_server

# Define a custom tool
class CalculatorTool(Tool):
    name = "calculator"

    def add(self, x: int, y: int) -> int:
        """Add two integers."""
        return x + y

    def multiply(self, x: int, y: int) -> int:
        """Multiply two integers."""
        return x * y

# Instantiate the Anthropic client
client = Anthropic(api_key=os.environ["ANTHROPIC_API_KEY"])

# Create the MCP server with the Claude model and the custom tool
server = Server(
    client=client,
    model="claude-3-5-sonnet-20241022",
    tools=[CalculatorTool()]
)

# Run the server using stdio transport
if __name__ == "__main__":
    stdio_server(server)

# Example: Using a different Claude model and multiple tools

from mcp.server import Server, Tool

class EchoTool(Tool):
    name = "echo"

    def repeat(self, message: str) -> str:
        return message

server = Server(
    client=client,
    model="claude-opus-4",
    tools=[CalculatorTool(), EchoTool()]
)

# Run with stdio_server(server) as before