Agent Skills Explained: How AI Agents Learn Step-by-Step Procedures

Agent skills are a way to give AI agents procedural knowledge, defined through a SKILL.md file containing a YAML frontmatter and a body of instructions. The frontmatter identifies the skill and describes when it should be used, acting as a trigger condition for the agent. To manage context efficiently, skills use progressive disclosure, loading only names and descriptions at startup and pulling full instructions only when a relevant task is detected. Unlike MCP, RAG, or fine-tuning, skills focus specifically on teaching agents how to perform tasks step by step, and the format has been adopted by platforms such as Claude and Codex. However, users are cautioned that skills can execute scripts, meaning malicious skills could pose security risks such as prompt injection or malware.