Building Custom MCP Servers with Next.js and mcp-handler

Model Context Protocol (MCP) enables LLMs to call your code directly instead of relying on manual copy-pasting or stale training data. This guide demonstrates building an MCP server using Next.js and mcp-handler that works across Claude Code, Gemini CLI, Cursor, and other MCP-compatible clients. Three practical tools are implemented: npm package lookup for version and download stats, GitHub repo stats for evaluating dependencies, and site uptime checking. The server uses tool descriptions to let LLMs automatically determine when to call each function, providing real-time data without context switching.