ExpressJS MCP

/** * Example 05: Re-register Tools Dynamically * * This example shows how to dynamically add, remove, and update MCP tools * at runtime without restarting the server. */ import express, { type Request, type Response } from "express"; import { z } from "zod"; import { ExpressMCP, type RouteInfo } from "../../src/index"; // Create base Express app const app = express(); app.use(express.json()); // Initial routes app.get("/health", (req: Request, res: Response) => { res.json({ status: "healthy", timestamp: new Date().toISOString() }); }); app.get("/api/v1/users", (req: Request, res: Response) => { res.json([ { id: 1, name: "Alice" }, { id: 2, name: "Bob" }, ]); }); // Create ExpressMCP instance const mcp = new ExpressMCP(app, { mountPath: "/mcp", logging: { info: (...args) => console.log("[MCP]", ...args), error: (...args) => console.error("[MCP ERROR]", ...args), }, }); // Track dynamically added routes const dynamicRoutes = new Map<string, any>(); // Admin endpoints to manage tools app.post("/admin/tools/add", async (req: Request, res: Response) => { const { path, method = "GET", handler, schema } = req.body; if (!path) { return res.status(400).json({ error: "Path is required" }); } const routeKey = `${method} ${path}`; // Check if route already exists if (dynamicRoutes.has(routeKey)) { return res.status(409).json({ error: "Route already exists" }); } // Create handler function const routeHandler = handler ? new Function("req", "res", handler) : (req: Request, res: Response) => { res.json({ message: `Dynamic route: ${method} ${path}`, timestamp: new Date().toISOString(), params: req.params, query: req.query, }); }; // Add route to Express const methodLower = method.toLowerCase() as keyof typeof app; if (["get", "post", "put", "delete", "patch"].includes(methodLower)) { (app as any)[methodLower](path, routeHandler); dynamicRoutes.set(routeKey, { path, method, handler: routeHandler, schema, }); // Re-initialize MCP to discover new route await mcp.init(); res.json({ message: "Tool added successfully", tool: routeKey, totalTools: mcp.listTools().length, }); } else { res.status(400).json({ error: "Invalid HTTP method" }); } }); app.delete("/admin/tools/remove", async (req: Request, res: Response) => { const { path, method = "GET" } = req.body; const routeKey = `${method} ${path}`; if (!dynamicRoutes.has(routeKey)) { return res.status(404).json({ error: "Route not found" }); } // Note: Express doesn't provide a clean way to remove routes // In production, you'd need to rebuild the router or use a more sophisticated approach dynamicRoutes.delete(routeKey); // Re-initialize MCP with filter to exclude removed route const originalExclude = mcp.options.exclude; mcp.options.exclude = (route: RouteInfo) => { const key = `${route.method} ${route.path}`; if (dynamicRoutes.has(key) && !dynamicRoutes.get(key)) { return true; // Exclude removed routes } return originalExclude ? originalExclude(route) : false; }; await mcp.init(); res.json({ message: "Tool removed successfully", tool: routeKey, totalTools: mcp.listTools().length, }); }); app.get("/admin/tools/list", (req: Request, res: Response) => { const tools = mcp.listTools(); const dynamicToolsList = Array.from(dynamicRoutes.keys()); res.json({ total: tools.length, static: tools.filter((t: any) => !dynamicToolsList.includes(t.title)) .length, dynamic: dynamicToolsList.length, tools: tools.map((t: any) => ({ name: t.name, title: t.title, isDynamic: dynamicToolsList.includes(t.title), })), }); }); app.post("/admin/tools/refresh", async (req: Request, res: Response) => { // Force re-initialization to discover any changes await mcp.init(); const tools = mcp.listTools(); res.json({ message: "Tools refreshed", totalTools: tools.length, tools: tools.map((t: any) => t.title), }); }); // Batch operations app.post("/admin/tools/batch", async (req: Request, res: Response) => { const { operations } = req.body; if (!Array.isArray(operations)) { return res.status(400).json({ error: "Operations must be an array" }); } const results = []; for (const op of operations) { const { action, path, method = "GET", handler, schema } = op; const routeKey = `${method} ${path}`; try { switch (action) { case "add": if (!dynamicRoutes.has(routeKey)) { const routeHandler = handler ? new Function("req", "res", handler) : (req: Request, res: Response) => { res.json({ message: `Dynamic route: ${method} ${path}`, timestamp: new Date().toISOString(), }); }; const methodLower = method.toLowerCase() as keyof typeof app; (app as any)[methodLower](path, routeHandler); dynamicRoutes.set(routeKey, { path, method, handler: routeHandler, schema, }); results.push({ route: routeKey, status: "added" }); } else { results.push({ route: routeKey, status: "already_exists" }); } break; case "remove": if (dynamicRoutes.has(routeKey)) { dynamicRoutes.delete(routeKey); results.push({ route: routeKey, status: "removed" }); } else { results.push({ route: routeKey, status: "not_found" }); } break; default: results.push({ route: routeKey, status: "invalid_action" }); } } catch (error) { results.push({ route: routeKey, status: "error", error: (error as Error).message, }); } } // Re-initialize MCP after batch operations await mcp.init(); res.json({ message: "Batch operations completed", results, totalTools: mcp.listTools().length, }); }); // Example: Add tools based on configuration app.post("/admin/tools/load-config", async (req: Request, res: Response) => { const { config } = req.body; const exampleConfig = config || [ { path: "/api/v2/products", method: "GET" }, { path: "/api/v2/products/:id", method: "GET" }, { path: "/api/v2/products", method: "POST" }, { path: "/api/v2/orders", method: "GET" }, { path: "/api/v2/orders/:id", method: "GET" }, ]; for (const route of exampleConfig) { const routeKey = `${route.method} ${route.path}`; if (!dynamicRoutes.has(routeKey)) { const handler = (req: Request, res: Response) => { res.json({ endpoint: routeKey, timestamp: new Date().toISOString(), params: req.params, query: req.query, }); }; const methodLower = route.method.toLowerCase() as keyof typeof app; (app as any)[methodLower](route.path, handler); dynamicRoutes.set(routeKey, { ...route, handler }); } } await mcp.init(); res.json({ message: "Configuration loaded", routesAdded: exampleConfig.length, totalTools: mcp.listTools().length, }); }); async function start() { await mcp.init(); mcp.mount(); const PORT = process.env.PORT || 3005; app.listen(PORT, () => { console.log(`✅ Express server running on http://localhost:${PORT}`); console.log(`📡 MCP tools available at http://localhost:${PORT}/mcp/tools`); console.log("\n🔧 Dynamic Tool Management:"); console.log(" POST /admin/tools/add - Add a new tool"); console.log(" DELETE /admin/tools/remove - Remove a tool"); console.log(" GET /admin/tools/list - List all tools"); console.log(" POST /admin/tools/refresh - Refresh tool discovery"); console.log(" POST /admin/tools/batch - Batch operations"); console.log(" POST /admin/tools/load-config - Load from config"); console.log("\n📝 Test Commands:"); console.log("\n1. Add a dynamic tool:"); console.log(` curl -X POST http://localhost:${PORT}/admin/tools/add \\`); console.log(` -H "Content-Type: application/json" \\`); console.log(` -d '{"path": "/api/dynamic/test", "method": "GET"}'`); console.log("\n2. Load example configuration:"); console.log( ` curl -X POST http://localhost:${PORT}/admin/tools/load-config \\`, ); console.log(` -H "Content-Type: application/json" \\`); console.log(` -d '{}'`); console.log("\n3. List all tools:"); console.log(` curl http://localhost:${PORT}/admin/tools/list`); console.log("\n4. Test dynamic tool via MCP:"); console.log(` curl -X POST http://localhost:${PORT}/mcp/invoke \\`); console.log(` -H "Content-Type: application/json" \\`); console.log(` -d '{"toolName": "GET_/api/dynamic/test", "args": {}}'`); }); } start().catch(console.error);