If you work with AI coding agents, you have probably seen SKILL.md mentioned and wondered what it actually is. In a matter of months it went from one company's feature to a standard adopted across Claude Code, Cursor, Codex CLI, Gemini CLI and more. Here is the plain explanation, with no hype.
What a skill actually is
A skill is a folder containing a SKILL.md file that teaches an AI agent to do a specific task well. Instead of re-explaining your conventions, your workflow, or your standards every single session, you write them down once. The agent reads them automatically whenever they are relevant.
Think of it as the onboarding note you would give a capable colleague taking over a task — except you write it once, and every agent that supports the standard reads it.
Why it caught on
