Instruction files that teach an AI agent how to do a specific task — like generating financial reports in your company's format, reviewing legal contracts, or building a web scraper. Each skill is a small package of step-by-step instructions and resources that the agent loads only when it needs them.

Where Model Context Protocol servers connect an agent to outside data and tools (the what), skills teach it workflows and best practices (the how). The two often work together: a skill might instruct an agent on how to analyze stock performance, while an MCP server connects it to live market data.

The format was originally developed by Anthropic for Claude Code and released as an open standard. It has since been adopted by other AI tools including GitHub Copilot, Cursor, and OpenAI's Codex.