Building Your First MCP Server: From Zero to AI-Powered Enterprise Tools

// Manual integration - developer writes code const weatherData = await fetch(https://api.weather.com/v1/weather?q=${city}); const result = await weatherData.json(); // AI can't discover or use this automatically 

// AI agent discovers and uses tools automatically server.tool('get-weather', 'Get weather for any city', { city: z.string().describe("City name") }, async ({ city }) => { // AI can discover, understand, and call this tool return { content: [{ type: "text", text: weatherResult }] }; }); 

mkdir enterprise-mcp-server cd enterprise-mcp-server npm init -y 

npm install express morgan dotenv zod @modelcontextprotocol/sdk 

OPENWEATHER_API_KEY=your_api_key_here PORT=3001 NODE_ENV=development 

import express from "express"; import "dotenv/config"; import logger from "morgan"; import { McpServer, ResourceTemplate, } from "@modelcontextprotocol/sdk/server/mcp.js"; import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js"; import { z } from "zod"; import { randomUUID } from "node:crypto"; console.log("Environment Variables:", { OPENWEATHER_API_KEY: process.env.OPENWEATHER_API_KEY ? "✅ Found" : "❌ Not Found", PORT: process.env.PORT, NODE_ENV: process.env.NODE_ENV }); // Map to store transports by session ID const transports = {}; // Function to create a new MCP server instance function createMcpServer() { const server = new McpServer({ name: "enterprise-mcp-demo-server", version: "1.0.0", }); // Weather Tool - AI can get real-time weather data server.tool( "get-weather", "Get current weather information for any location", { location: z.string().describe("City name, state/country (e.g., 'London', 'New York,US')"), units: z.enum(["standard", "metric", "imperial"]).optional().describe("Temperature units") }, async ({ location, units = "metric" }) => { try { const apiKey = process.env.OPENWEATHER_API_KEY; if (!apiKey) { return { content: [{ type: "text", text: "❌ OpenWeatherMap API key not configured. Please add OPENWEATHER_API_KEY to your environment variables." }] }; } const response = await fetch( `https://api.openweathermap.org/data/2.5/weather?q=${encodeURIComponent(location)}&appid=${apiKey}&units=${units}` ); if (!response.ok) { throw new Error(`Weather API error: ${response.status}`); } const data = await response.json(); const tempUnit = units === "metric" ? "°C" : units === "imperial" ? "°F" : "K"; return { content: [{ type: "text", text: `🌤️ **Weather in ${data.name}, ${data.sys.country}:** Temperature: ${data.main.temp}${tempUnit} (feels like ${data.main.feels_like}${tempUnit}) Description: ${data.weather.description} Humidity: ${data.main.humidity}% Wind: ${data.wind.speed} m/s }] }; } catch (error) { return { content: [{ type: "text", text:❌ Error fetching weather: ${error.message}` }] }; } } ); // Team Productivity Analysis Tool - Enterprise Demo server.tool( "analyze-team-productivity", "Analyze team productivity and get AI-powered insights", { teamName: z.string().describe("Team name to analyze"), timeframe: z.enum(["today", "week", "month"]).describe("Analysis timeframe") }, async ({ teamName, timeframe }) => { // Simulate real business logic const mockData = { meetings: timeframe === "today" ? 4 : timeframe === "week" ? 28 : 120, focusTime: timeframe === "today" ? 6.5 : timeframe === "week" ? 32 : 140, blockers: ["API integration delays", "Code review bottleneck", "Meeting overload"], suggestions: ["Block 2hr focus time daily", "Implement async code reviews", "Reduce meetings by 30%"] }; return { content: [{ type: "text", text: `📊 **${teamName} Team Analysis (${timeframe})** 🎯 Key Metrics: Meetings: ${mockData.meetings}h Deep Focus Time: ${mockData.focusTime}h Productivity Score: ${Math.round((mockData.focusTime / (mockData.meetings + mockData.focusTime)) * 100)}% ⚠️ Current Blockers: ${mockData.blockers.map(b => - ${b}).join('\n')} 💡 AI Recommendations: ${mockData.suggestions.map(s => - ${s}).join('\n')} 🚀 Estimated Impact: +25% team velocity, -40% context switching` }] }; } ); // Business ROI Calculator Tool server.tool( "calculate-mcp-roi", "Calculate ROI of implementing MCP across the organization", { teamSize: z.number().describe("Number of team members"), currentProcesses: z.number().describe("Number of manual processes"), avgHourlyRate: z.number().optional().describe("Average hourly rate (default: $50)") }, async ({ teamSize, currentProcesses, avgHourlyRate = 50 }) => { const hoursPerProcess = 2; const automationRate = 0.7; // 70% can be automated const monthlyHours = teamSize * currentProcesses * hoursPerProcess; const currentMonthlyCost = monthlyHours * avgHourlyRate; const automatedHours = monthlyHours * automationRate; const monthlySavings = automatedHours * avgHourlyRate; const implementationCost = 10000; const monthlyMaintenance = 1000; const breakEvenMonths = Math.ceil(implementationCost / (monthlySavings - monthlyMaintenance)); return { content: [{ type: "text", text: `💰 **MCP ROI Analysis for ${teamSize}-person team** 📊 Current State: Manual Processes: ${currentProcesses} Hours/Month: ${monthlyHours.toLocaleString()} Current Cost: $${currentMonthlyCost.toLocaleString()}/month 🤖 With MCP (70% automation): Monthly Savings: $${monthlySavings.toLocaleString()} Annual Savings: $${(monthlySavings * 12).toLocaleString()} Break-even: ${breakEvenMonths} months 🚀 3-Year ROI: ${Math.round(((monthlySavings * 36) / implementationCost) * 100)}%` }] }; } ); return server; } const port = process.env.PORT || 3001; const app = express(); app.use(logger("dev")); app.use(express.json()); // CORS headers for MCP compatibility app.use((req, res, next) => { res.header('Access-Control-Allow-Origin', '*'); res.header('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, DELETE'); res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, mcp-session-id'); if (req.method === 'OPTIONS') { res.sendStatus(200); } else { next(); } }); // Health check endpoint app.get("/", (req, res) => { res.json({ message: "🚀 Enterprise MCP Demo Server is running!", version: "1.0.0", tools: 3, capabilities: [ "Real-time Weather Data", "Team Productivity Analysis", "ROI Calculations", "AI Agent Integration" ], endpoints: { health: "/", mcp: "/mcp" }, transport: "StreamableHTTP" }); }); // MCP endpoint handler app.post("/mcp", async (req, res) => { console.log("MCP Request:", { sessionId: req.headers["mcp-session-id"], method: req.body?.method }); const sessionId = req.headers["mcp-session-id"]; let transport; if (sessionId && transports[sessionId]) { transport = transports[sessionId]; } else if (!sessionId || req.body?.method === "initialize") { transport = new StreamableHTTPServerTransport({ sessionIdGenerator: () => randomUUID(), onsessioninitialized: (newSessionId) => { transports[newSessionId] = transport; console.log("✅ Session initialized:", newSessionId); }, enableDnsRebindingProtection: false, }); transport.onclose = () => { if (transport.sessionId) { console.log("🧹 Cleaning up session:", transport.sessionId); delete transports[transport.sessionId]; } }; const server = createMcpServer(); await server.connect(transport); } else { res.status(400).json({ jsonrpc: "2.0", error: { code: -32000, message: "Invalid session ID" }, id: null, }); return; } try { await transport.handleRequest(req, res, req.body); } catch (error) { console.error("❌ MCP Error:", error); res.status(500).json({ jsonrpc: "2.0", error: { code: -32603, message: "Internal error" }, id: null, }); } }); // Handle GET requests for server-to-client notifications via SSE app.get("/mcp", async (req, res) => { const sessionId = req.headers["mcp-session-id"]; if (!sessionId || !transports[sessionId]) { res.status(400).send("Invalid session ID"); return; } try { await transports[sessionId].handleRequest(req, res); } catch (error) { console.error("❌ SSE Error:", error); res.status(500).send("Internal server error"); } }); app.listen(port, () => { console.log(🚀 Enterprise MCP Server running on port ${port}); console.log(🔗 Health check: http://localhost:${port}); console.log(⚡ MCP endpoint: http://localhost:${port}/mcp); console.log(📊 Available tools: 3); //tools length });` 

{ "servers": { "enterprise-mcp-demo": { "url": "http://localhost:3001/mcp", "type": "http", "dev": { "watch": "**/*.js", "debug": { "type": "node" } } } } } 

node app.js 

curl http://localhost:3001 

curl -X POST http://localhost:3001/mcp -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"capabilities":{},"clientInfo":{"name":"test","version":"1.0.0"}}}' 

// Session storage const transports = {}; // Create transport for new sessions transport = new StreamableHTTPServerTransport({ sessionIdGenerator: () => randomUUID(), onsessioninitialized: (newSessionId) => { transports[newSessionId] = transport; // Store session }, enableDnsRebindingProtection: false, // Dev mode }); // Cleanup on disconnect transport.onclose = () => { delete transports[transport.sessionId]; }; 

erver.tool("get-weather", "Get current weather information for any location", ...) 

server.tool("data", "Gets stuff", ...) 

// ✅ Good: Proper error handling try { const result = await externalAPI(); return { content: [{ type: "text", text: result }] }; } catch (error) { return { content: [{ type: "text", text: ❌ Error: ${error.message} }] }; } // ✅ Good: Input validation with Zod { email: z.string().email().describe("Valid email address"), amount: z.number().positive().describe("Positive dollar amount") } 

const apiKey = process.env.OPENWEATHER_API_KEY; 

if (!apiKey) { throw new Error("Missing required API key"); } // ✅ Never expose secrets in responses API Key: ${apiKey.substring(0, 8)}... // First 8 chars only 

Production .env NODE_ENV=production PORT=3001 OPENWEATHER_API_KEY=your_production_key 

import compression from 'compression'; app.use(compression()); 

import rateLimit from 'express-rate-limit'; app.use(rateLimit({ windowMs: 15 * 60 * 1000, // 15 minutes max: 100 // limit each IP to 100 requests per windowMs })); 

app.use(timeout('30s')); 

FROM node:18-alpine WORKDIR /app COPY package*.json ./ RUN npm ci --only=production COPY . . EXPOSE 3001 CMD ["node", "app.js"] 

server.tool("query-database", "Execute SQL queries", ...) 

server.tool("send-slack-message", "Send team notifications", ...) 

server.tool("schedule-meeting", "Book meetings automatically", ...) 

server.tool("analyze-document", "Extract insights from PDFs", ...)