mini MCP server

mini.py

#!/usr/bin/env uv run
# /// script
# requires-python = ">=3.11"
# dependencies = [
#     "mcp",
# ]
# ///
'''
    claude mcp add mini $PWD/mini.py

    claude --allowedTools mcp__mini__add -p "add numbers 2 & 3, 4 & 5, 6 & 7 with the mini mcp"
    cat mini_output.txt
    # [pid: 51155] Starting mini MCP server
    # [pid: 51155] 2 + 3 = 5
    # [pid: 51155] 4 + 5 = 9
    # [pid: 51155] 6 + 7 = 13

    claude
    # add numbers 2 & 3, 4 & 5, 6 & 7 with the mini mcp
    cat mini_output.txt
    # [pid: 54051] Starting mini MCP server
    # [pid: 54839] Starting mini MCP server
    # [pid: 54841] Starting mini MCP server
    # [pid: 54841] 2 + 3 = 5
    # [pid: 54862] Starting mini MCP server
    # [pid: 54934] Starting mini MCP server
    # [pid: 54934] 4 + 5 = 9
    # [pid: 54956] Starting mini MCP server
    # [pid: 54958] Starting mini MCP server
    # [pid: 54958] 6 + 7 = 13
'''
import fcntl
import sys
import os
from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Demo")

output_file = "mini_output.txt"

def log(message: str) -> None:
    with open(output_file, "a") as f:
        fcntl.flock(f.fileno(), fcntl.LOCK_EX)
        try:
            f.write(f"[pid: {os.getpid()}] {message}\n")
        finally:
            fcntl.flock(f.fileno(), fcntl.LOCK_UN)

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers"""

    res = a + b
    log(f"{a} + {b} = {res}")
    return res

if __name__ == "__main__":
    print(f"Output will be written to {output_file}", file=sys.stderr)  # noqa: T201
    log("Starting mini MCP server")
    mcp.run(transport="stdio")