Build an MCP Server: Complete Tutorial (Python & TypeScript)

# server.py - FastMCP MCP Server
from fastmcp import FastMCP

mcp = FastMCP("my-server")

@mcp.tool()
def get_weather(city: str) -> dict:
    """Get current weather for a city."""
    # Your API call here
    return {"city": city, "temp": 22, "condition": "sunny"}

@mcp.tool()
def calculate(a: float, b: float, op: str = "add") -> float:
    """Perform calculation: add, sub, mul, div."""
    ops = {"add": a + b, "sub": a - b, "mul": a * b, "div": a / b}
    return ops.get(op, a + b)

@mcp.resource("config://settings")
def get_settings() -> str:
    """Server configuration."""
    return "max_requests: 100\nversion: 1.0.0"

if __name__ == "__main__":
    mcp.run()

// server.ts - TypeScript MCP Server
import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { CallToolRequestSchema, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";

const server = new Server(
  { name: "my-server", version: "1.0.0" },
  { capabilities: { tools: {} } }
);

// Define tools
server.setRequestHandler(ListToolsRequestSchema, async () => ({
  tools: [{
    name: "get_weather",
    description: "Get weather for a city",
    inputSchema: {
      type: "object",
      properties: { city: { type: "string" } },
      required: ["city"]
    }
  }]
}));

// Handle tool calls
server.setRequestHandler(CallToolRequestSchema, async (request) => {
  const { name, arguments: args } = request.params;
  if (name === "get_weather") {
    return {
      content: [{ type: "text", text: `Weather in ${args?.city}: 22°C, sunny` }]
    };
  }
  throw new Error(`Unknown tool: ${name}`);
});

// Start server
const transport = new StdioServerTransport();
await server.connect(transport);