Agent Skills are portable folders of instructions, scripts, and resources that agents discover and load on demand. They follow the Agent Skills open standard and work across 27+ compatible agents including Claude Code, Cursor, Gemini CLI, OpenAI Codex, VS Code, GitHub Copilot, Windsurf, Goose, and Roo Code. This skill covers the complete workflow for creating, structuring, and validating skills.
| Directory structure | skill-name/SKILL.md plus optional references/, scripts/, assets/ | SKILL.md is the only required file | | Frontmatter (required) | YAML block with name and description | name must match directory, max 64 chars |
| Frontmatter (optional) | license, compatibility, metadata, allowed-tools | Defined by open standard, portable across agents | | Agent-specific fields | model, context, agent, hooks, user-invocable | Claude Code extensions, not portable | | Description triggers | Include "Use when..." or "Use for..." phrases | Keyword-rich, third-person voice |