Skills and Hooks

Skills

What They Are

Markdown files that extend Claude Code's capabilities. A skill is a structured prompt template — it tells Claude Code how to do something.

Where They Live

~/.claude/skills/          # Global skills (available everywhere)
.claude/skills/            # Project skills (checked into git)

Anatomy of a Skill

---
description: Short description shown in skill list
user_invocable: true       # Can be called with /skill-name
---

# Skill Name

## When to Use
[Conditions for invoking this skill]

## Process
[Step-by-step instructions]

## Templates
[Code templates, file structures, etc.]

Skills I Use

Skill	What It Does
awesome-list-builder	Full pipeline for creating awesome lists + MkDocs sites
subagent-driven-development	Execute plans via fresh subagent per task with two-stage review
writing-plans	Create detailed implementation plans with TDD
code-reviewer	Review implementation against plan and standards

Key Insight

Skills are codified expertise. Instead of explaining your workflow every session, write it once as a skill. The skill becomes part of your toolbox permanently.

Hooks

What They Are

Shell commands that run automatically in response to Claude Code events.

Configuration

In ~/.claude/settings.json or .claude/settings.json:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write",
        "command": "echo 'About to write a file'"
      }
    ],
    "PostToolUse": [
      {
        "matcher": "Bash",
        "command": "echo 'Command executed'"
      }
    ]
  }
}

Event Types

Event	When	Use Case
PreToolUse	Before a tool runs	Validation, confirmation
PostToolUse	After a tool runs	Auto-format, lint, notify
Notification	On notification	Desktop alerts, Slack messages

Practical Examples

Auto-format Python files after write:

{
  "PostToolUse": [{
    "matcher": "Write",
    "command": "if [[ \"$TOOL_INPUT\" == *.py ]]; then ruff format \"$TOOL_INPUT\"; fi"
  }]
}

Block writes to sensitive files:

{
  "PreToolUse": [{
    "matcher": "Write",
    "command": "if [[ \"$TOOL_INPUT\" == *.env* ]]; then echo 'BLOCKED: cannot write .env files' >&2; exit 1; fi"
  }]
}

Skills + Hooks Together

Skills define what to do. Hooks automate the surrounding workflow. Together they make Claude Code sessions consistent and efficient.