Building a Minimal MCP Server

An MCP server exposes tools over stdio or HTTP. Any MCP-capable client (Claude Desktop, Cursor, Claude Code) can call them. Build once, use everywhere.

npm install @modelcontextprotocol/sdk zod

// server.ts
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

const server = new McpServer({
  name: "word-tools",
  version: "0.1.0",
});

server.tool(
  "word_count",
  "Count words in a string.",
  { text: z.string().min(1) },
  async ({ text }) => {
    const count = text.trim().split(/\s+/).length;
    return {
      content: [{ type: "text", text: String(count) }],
    };
  }
);

server.tool(
  "reverse",
  "Reverse a string.",
  { text: z.string() },
  async ({ text }) => ({
    content: [{ type: "text", text: [...text].reverse().join("") }],
  })
);

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

// claude_desktop_config.json snippet
{
  "mcpServers": {
    "word-tools": {
      "command": "node",
      "args": ["/absolute/path/to/server.js"]
    }
  }
}

Understanding "Building a Minimal MCP Server" in practice: AI-assisted coding shifts work from syntax recall to design thinking — models handle boilerplate so you focus on architecture. Model Context Protocol lets agents plug into your tools. A 40-line server exposes a real capability to Claude — and knowing how to apply this gives you a concrete advantage.

• Apply MCP in your ai-coding workflow to get better results
• Apply tools in your ai-coding workflow to get better results
• Apply stdio transport in your ai-coding workflow to get better results
• Apply schema in your ai-coding workflow to get better results

1. 1Use AI to generate unit tests for an existing function
2. 2Ask AI to refactor a messy function and explain the changes
3. 3Have AI suggest a code review for a recent pull request

The big idea: MCP is the USB port for agents. Write a tiny server once, and every MCP client can use your tools.