Skills - Modular capabilities in SKILL.md files that provide domain expertise
Hooks - Event-driven automation that executes on tool use and session events
Slash Commands - Reusable prompts triggered with /command-name syntax
Subagents - Specialized Claude instances for delegated tasks

All four extension types share core principles: pure XML structure, YAML frontmatter, and clear success criteria. This skill teaches you to create effective extensions following best practices.

Skill - SKILL.md file for domain expertise
Hook - Event-driven automation (PreToolUse, PostToolUse, Stop, etc.)
Slash Command - Reusable prompt with /command-name
Subagent - Specialized agent for delegated tasks
Guidance - Help deciding which extension type to use

extension-authoring