Build a minimal MCP server with tools using the official TypeScript SDK (v2) and run it over stdio

Documented steps

1. Init the project: mkdir myserver && cd myserver && npm init -y && npm pkg set type=module && npm install @modelcontextprotocol/server zod tsx — 'type=module' is required because the v2 SDK ships ES modules only. Docs: https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/docs/get-started/first-server.md
2. In src/index.ts import { McpServer } from '@modelcontextprotocol/server', { serveStdio } from '@modelcontextprotocol/server/stdio', and import * as z from 'zod/v4' (Zod v4 is the documented default).
3. Write a createServer() factory: const server = new McpServer({ name: 'myserver', version: '1.0.0' }); then server.registerTool('tool-name', { description: '...', inputSchema: z.object({ arg: z.string() }) }, async ({ arg }) => ({ content: [{ type: 'text', text: '...' }] })); return server; — registerTool takes (name, config, handler); the SDK derives JSON Schema from the Zod schema, validates arguments before the handler runs, and infers handler argument types.
4. Serve it: at the bottom call void serveStdio(createServer); optionally console.error('running on stdio') — serveStdio owns the stdio transport and calls the factory once per connection. See https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/docs/serving/stdio.md
5. Run with npx tsx src/index.ts (no build step). The process waits silently on stdin until a client connects — this is expected, not a hang.
6. Test without writing a client: npx @modelcontextprotocol/inspector npx tsx src/index.ts, then connect in the browser UI, open Tools, and run your tool.