Understanding Model Context Protocol (MCP) for Developers

from mcp import Server, Tool
import os

class DevToolsServer(Server):
    def __init__(self):
        super().__init__("dev-tools")
        self.register_tools()

    def register_tools(self):
        @self.tool("read_file")
        def read_file(path: str) -> str:
            """Read contents of a file safely"""
            if not os.path.exists(path):
                return "File not found"

            with open(path, 'r') as f:
                return f.read()

        @self.tool("list_directory")
        def list_directory(path: str) -> list:
            """List files in directory"""
            try:
                return os.listdir(path)
            except OSError:
                return []

        @self.tool("run_command")
        def run_command(cmd: str) -> str:
            """Execute shell command safely"""
            import subprocess
            allowed_commands = ['ls', 'git', 'npm', 'python']

            if not any(cmd.startswith(allowed) for allowed in allowed_commands):
                return "Command not allowed"

            result = subprocess.run(cmd.split(), capture_output=True, text=True)
            return f"Exit code: {result.returncode}\n{result.stdout}\n{result.stderr}"

# Start server
server = DevToolsServer()
server.run(port=8000)

import requests

def query_mcp_server(tool_name, **kwargs):
    response = requests.post(
        "http://localhost:8000/tools/invoke",
        json={"tool": tool_name, "arguments": kwargs}
    )
    return response.json()

# Usage
files = query_mcp_server("list_directory", path="./src")
content = query_mcp_server("read_file", path="./package.json")