Building an MCP server with Node.js

The Model Context Protocol (MCP) is an open standard for connecting AI hosts (Claude, ChatGPT, Cursor, VS Code, and others) to external context and actions through a structured protocol instead of ad-hoc plugins.

The host runs an MCP client. Your application is the MCP server, exposing tools (actions the model can invoke), resources (read-only data), and optionally prompts (reusable message templates). Communication uses JSON-RPC over a transport such as stdio or HTTP.

This post shows how to build a small todo MCP server with Node.js using the official @modelcontextprotocol/sdk package and Zod schemas.

Architecture at a glance

sequenceDiagram