4.2 MCP 协议深度解析：标准架构与 JSON-RPC 规范

// server.ts
import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
import {
  CallToolRequestSchema,
  ListToolsRequestSchema,
} from '@modelcontextprotocol/sdk/types.js';
import * as os from 'os';
 
// 1. 初始化 MCP 服务端元数据
const server = new Server(
  {
    name: 'system-diagnostic-mcp-server',
    version: '1.0.0',
  },
  {
    capabilities: {
      tools: {}, // 声明具备工具暴露能力
    },
  }
);
 
// 2. 注册可用工具列表 (tools/list 响应)
server.setRequestHandler(ListToolsRequestSchema, async () => {
  return {
    tools: [
      {
        name: 'get_system_metrics',
        description: '获取当前服务器或本机的 CPU 核心数、内存使用率与系统负载',
        inputSchema: {
          type: 'object',
          properties: {
            detailed: {
              type: 'boolean',
              description: '是否返回详细的网络接口信息',
            },
          },
        },
      },
    ],
  };
});
 
// 3. 实现工具具体执行逻辑 (tools/call 响应)
server.setRequestHandler(CallToolRequestSchema, async (request) => {
  if (request.params.name === 'get_system_metrics') {
    const totalMem = os.totalmem();
    const freeMem = os.freemem();
    const usedMemPercent = (((totalMem - freeMem) / totalMem) * 100).toFixed(2);
 
    const metrics = {
      platform: os.platform(),
      cpus: os.cpus().length,
      freeMemoryMB: Math.round(freeMem / 1024 / 1024),
      usedMemoryPercent: `${usedMemPercent}%`,
      loadAvg: os.loadavg(),
    };
 
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(metrics, null, 2),
        },
      ],
    };
  }
 
  throw new Error(`未知的工具调用指令: ${request.params.name}`);
});
 
// 4. 绑定标准输入输出传输通道并启动
async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
  console.error('[System Diagnostic MCP] 服务已成功通过 Stdio 通道就绪运行');
}
 
main().catch((err) => {
  console.error('MCP Server 启动失败:', err);
  process.exit(1);
});