Agent Skills: building-skills

Expert at creating and modifying Claude Code skills. Auto-invokes when the user wants to create, update, modify, enhance, validate, or standardize skills, or when modifying skill YAML frontmatter fields (especially 'allowed-tools', 'description'), needs help designing skill architecture, or wants to understand when to use skills vs agents. Also auto-invokes proactively when Claude is about to write skill files (*/skills/*/SKILL.md), create skill directory structures, or implement tasks that involve creating skill components.