MCP Coordinator

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"; import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"; import { Client } from "@modelcontextprotocol/sdk/client/index.js"; import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js"; import { CallToolResultSchema } from "@modelcontextprotocol/sdk/types.js"; import { z } from "zod"; import { spawn, ChildProcess } from "child_process"; import { readFileSync } from "fs"; import { fileURLToPath } from "url"; import { dirname, join } from "path"; // Get directory of this file const __filename = fileURLToPath(import.meta.url); const __dirname = dirname(__filename); // Load manifest interface ServerConfig { description: string; command: string; args: string[]; env: Record<string, string>; } interface Manifest { servers: Record<string, ServerConfig>; } const manifestPath = join(__dirname, "manifest.json"); let manifest: Manifest; try { manifest = JSON.parse(readFileSync(manifestPath, "utf-8")); } catch (error) { console.error("Failed to load manifest.json:", error); process.exit(1); } // Active MCP client connections const activeClients: Map<string, { client: Client; process: ChildProcess }> = new Map(); // Initialize the coordinator server const server = new McpServer({ name: "mcp-coordinator", version: "1.0.0", }); // Tool 1: List available MCP servers server.tool( "list_mcps", "List all available MCP servers and their descriptions", {}, async () => { const serverList = Object.entries(manifest.servers).map(([name, config]) => ({ name, description: config.description, })); return { content: [ { type: "text", text: JSON.stringify(serverList, null, 2), }, ], }; } ); // Tool 2: Get tools available in a specific MCP server server.tool( "get_mcp_tools", "Get the list of tools available in a specific MCP server", { server_name: z.string().describe("Name of the MCP server (from list_mcps)"), }, async ({ server_name }) => { const config = manifest.servers[server_name]; if (!config) { return { content: [ { type: "text", text: `Error: Server "${server_name}" not found. Use list_mcps to see available servers.`, }, ], }; } try { // Connect to the MCP server const { client } = await connectToServer(server_name, config); // Get tools const toolsResult = await client.listTools(); const tools = toolsResult.tools.map((tool) => ({ name: tool.name, description: tool.description, inputSchema: tool.inputSchema, })); return { content: [ { type: "text", text: JSON.stringify(tools, null, 2), }, ], }; } catch (error) { return { content: [ { type: "text", text: `Error connecting to ${server_name}: ${error}`, }, ], }; } } ); // Tool 3: Call a tool on an MCP server server.tool( "call_mcp_tool", "Call a specific tool on an MCP server", { server_name: z.string().describe("Name of the MCP server"), tool_name: z.string().describe("Name of the tool to call"), tool_args: z.record(z.string(), z.unknown()).optional().describe("Arguments to pass to the tool (as JSON object)"), }, async ({ server_name, tool_name, tool_args }) => { const config = manifest.servers[server_name]; if (!config) { return { content: [ { type: "text", text: `Error: Server "${server_name}" not found.`, }, ], }; } try { // Connect to the MCP server (reuses existing connection if available) const { client } = await connectToServer(server_name, config); // Call the tool const result = await client.callTool( { name: tool_name, arguments: tool_args || {}, }, CallToolResultSchema ); // Format the result let resultText: string; if (Array.isArray(result.content)) { resultText = result.content .map((c) => (c.type === "text" ? c.text : JSON.stringify(c))) .join("\n"); } else { resultText = JSON.stringify(result.content); } return { content: [ { type: "text", text: resultText, }, ], }; } catch (error) { return { content: [ { type: "text", text: `Error calling ${tool_name} on ${server_name}: ${error}`, }, ], }; } } ); // Helper function to connect to an MCP server async function connectToServer( serverName: string, config: ServerConfig ): Promise<{ client: Client; process: ChildProcess }> { // Check if already connected const existing = activeClients.get(serverName); if (existing) { return existing; } // Prepare environment variables const env: Record<string, string> = { ...process.env } as Record<string, string>; for (const [key, value] of Object.entries(config.env)) { // Replace ${VAR} with actual environment variable const resolvedValue = value.replace(/\$\{(\w+)\}/g, (_, varName) => { return process.env[varName] || ""; }); env[key] = resolvedValue; } // Spawn the MCP server process const childProcess = spawn(config.command, config.args, { env, stdio: ["pipe", "pipe", "pipe"], shell: true, }); // Create MCP client const client = new Client({ name: "mcp-coordinator-client", version: "1.0.0", }); // Create transport const transport = new StdioClientTransport({ command: config.command, args: config.args, env, }); // Connect await client.connect(transport); // Store the connection activeClients.set(serverName, { client, process: childProcess }); // Handle process exit childProcess.on("exit", () => { activeClients.delete(serverName); }); return { client, process: childProcess }; } // Cleanup function async function cleanup() { for (const [name, { client, process }] of activeClients) { try { await client.close(); process.kill(); } catch (error) { console.error(`Error cleaning up ${name}:`, error); } } activeClients.clear(); } // Handle process signals process.on("SIGINT", async () => { await cleanup(); process.exit(0); }); process.on("SIGTERM", async () => { await cleanup(); process.exit(0); }); // Start the server async function main() { const transport = new StdioServerTransport(); await server.connect(transport); console.error("MCP Coordinator running on stdio"); } main().catch((error) => { console.error("Fatal error:", error); process.exit(1); });