# Hook Development

Should be used when the user asks to "create a hook", "add a...

- Repository: https://github.com/anthropics/claude-plugins-official (45706 stars)
- Category: AI and agents
- License: Apache-2.0
- Last updated: 2026-11-01
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add anthropics/claude-plugins-official --skill hook-development -g -a claude-code -y`
Codex: `npx skills add anthropics/claude-plugins-official --skill hook-development -g -a codex -y`
Cursor: `npx skills add anthropics/claude-plugins-official --skill hook-development -g -a cursor -y`
Gemini CLI: `npx skills add anthropics/claude-plugins-official --skill hook-development -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add anthropics/claude-plugins-official`

## Description

This skill should be used when the user asks to "create a hook", "add a PreToolUse/PostToolUse/Stop hook", "validate tool use", "implement prompt-based hooks", "use ${CLAUDE_PLUGIN_ROOT}", "set up event-driven automation", "block dangerous commands", or mentions hook events (PreToolUse, PostToolUse, Stop, SubagentStop, SessionStart, SessionEnd, UserPromptSubmit, PreCompact, Notification). Provides comprehensive guidance for creating and implementing Claude Code plugin hooks with focus on advanced prompt-based hooks API.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Hook Development for Claude Code Plugins

## Overview

Hooks are event-driven automation scripts that execute in response to Claude Code events. Use hooks to validate operations, enforce policies, add context, and integrate external tools into workflows.

**Key capabilities:**
- Validate tool calls before execution (PreToolUse)
- React to tool results (PostToolUse)
- Enforce completion standards (Stop, SubagentStop)
- Load project context (SessionStart)
- Automate workflows across the development lifecycle

## Hook Types

### Prompt-Based Hooks (Recommended)

Use LLM-driven decision making for context-aware validation:

```json
{
  "type": "prompt",
  "prompt": "Evaluate if this tool use is appropriate: $TOOL_INPUT",
  "timeout": 30
}
```

**Supported events:** Stop, SubagentStop, UserPromptSubmit, PreToolUse

**Benefits:**
- Context-aware decisions based on natural language reasoning
- Flexible evaluation logic without bash scripting
- Better edge case handling
- Easier to maintain and extend

### Command Hooks

Execute bash commands for deterministic checks:

```json
{
  "type": "command",
  "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/validate.sh",
  "timeout": 60
}
```

**Use for:**
- Fast deterministic validations
- File system operations
- External tool integrations
- Performance-critical checks

## Hook Configuration Formats

### Plugin hooks.json Format

**For plugin hooks** in `hooks/hooks.json`, use wrapper format:

```json
{
  "description": "Brief explanation of hooks (optional)",
  "hooks": {
    "PreToolUse": [...],
    "Stop": [...],
    "SessionStart": [...]
  }
}
```

**Key points:**
- `description` field is optional
- `hooks` field is required wrapper containing actual hook events
- This is the **plugin-specific format**

The rest: https://github.com/anthropics/claude-plugins-official/blob/HEAD/plugins/plugin-dev/skills/hook-development/SKILL.md