Agent skills are markdown files that encode repeatable developer workflows and load automatically into AI coding assistants like Claude Code, GitHub Copilot, Cursor, and Gemini CLI. A skill consists of a SKILL.md file with YAML frontmatter (name and description) and a markdown body with instructions. The tutorial walks through building a commit-message-writer skill that reads staged git changes and generates Conventional Commits-formatted messages. Key lessons include writing effective description fields with trigger phrases to ensure the skill loads reliably, structuring instructions to produce consistent output formats, testing edge cases, and iterating on the skill over time. The same SKILL.md format works across all major AI coding tools.
