How do I install the Hook Development skill?

Run npx skillmds@latest add lucassantana-dev/hook-development in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Hook Development safe to use?

This skill has not completed SkillMD's automated safety review yet. Independent scanners report: SkillSpector: PASS, Skill Scanner: PASS. Capability flags: reads secrets. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Hook Development?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Hook Development free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Hook Development?

LucasSantana-Dev (@lucassantana-dev) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Hook Development by lucassantana-dev

Name: Hook Development
Rating: 4.2 (5 reviews)
Author: LucasSantana-Dev

Hook Development

Use when creating hooks for Claude Code plugins. Covers hook events, configuration, exit codes, and stdin/stdout contracts. Hooks execute in response to events to validate operations and enforce policies.

LucasSantana-Dev Updated Aug 19, 2026 1 repo stars

File contents

Hook Development for Claude Code Plugins

Hooks are event-driven scripts that validate operations, enforce policies, and add context.

Hook Types

Prompt-based (LLM reasoning): Use for complex validation. Recommended.

{"type": "prompt", "prompt": "Validate write safety. Check for: system paths, secrets, path traversal.", "timeout": 30}

Command (bash): Use for deterministic checks, fast operations.

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

Hook Events

Event	When	Use
PreToolUse	Before tool	Approve/deny/modify calls
PostToolUse	After tool	React to results, log
UserPromptSubmit	User prompt	Add context, validate
Stop	Agent stopping	Verify completion
SubagentStop	Subagent done	Ensure task complete
SessionStart	Session begins	Load context, env vars

Configuration

Plugin: hooks/hooks.json (with "hooks" wrapper)

{"hooks": {"PreToolUse": [...]}}

User settings: .claude/settings.json (direct, no wrapper)

{"PreToolUse": [...]}

Exit Codes

0 — Success; stdout in transcript
2 — Block; stderr to Claude (halt)

Prompt hooks return JSON: {decision: approve|block|ask}

stdin/stdout Contract

Input JSON includes tool_name, tool_input (PreToolUse), user_prompt (UserPromptSubmit), etc.

Output JSON:

{"continue": true, "systemMessage": "..."}

Example: Write Validation

{
  "PreToolUse": [{
    "matcher": "Write|Edit",
    "hooks": [{"type": "command", "command": "bash ${CLAUDE_PLUGIN_ROOT}/hooks/validate.sh"}]
  }]
}

Script:

#!/bin/bash
input=$(cat)
file=$(echo "$input" | jq -r '.tool_input.file_path')

[[ "$file" == *".."* ]] && echo '{"decision":"deny"}' >&2 && exit 2
[[ "$file" == *".env"* ]] && echo '{"decision":"deny"}' >&2 && exit 2

echo '{"decision":"approve"}'

Critical Rules

Quote all bash variables: "$var" not $var
Use ${CLAUDE_PLUGIN_ROOT} for portability
Set timeouts: command 60s, prompt 30s
Validate all inputs
Hooks load at session start — restart to apply changes

See REFERENCE.md for: full event catalog, matcher patterns, testing, environment variables.

---name: hook-developmentdescription: Use when creating hooks for Claude Code plugins. Covers hook events, configuration, exit codes, and stdin/stdout contracts. Hooks execute in response to events to validate operations and enforce policies.---# Hook Development for Claude Code PluginsHooks are event-driven scripts that validate operations, enforce policies, and add context.## Hook Types**Prompt-based** (LLM reasoning): Use for complex validation. Recommended.```json{"type": "prompt", "prompt": "Validate write safety. Check for: system paths, secrets, path traversal.", "timeout": 30}```**Command** (bash): Use for deterministic checks, fast operations.```json{"type": "command", "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/validate.sh", "timeout": 60}```## Hook Events| Event | When | Use ||-------|------|-----|| PreToolUse | Before tool | Approve/deny/modify calls || PostToolUse | After tool | React to results, log || UserPromptSubmit | User prompt | Add context, validate || Stop | Agent stopping | Verify completion || SubagentStop | Subagent done | Ensure task complete || SessionStart | Session begins | Load context, env vars |## Configuration**Plugin:** `hooks/hooks.json` (with `"hooks"` wrapper)```json{"hooks": {"PreToolUse": [...]}}```**User settings:** `.claude/settings.json` (direct, no wrapper)```json{"PreToolUse": [...]}```## Exit Codes- **0** — Success; stdout in transcript- **2** — Block; stderr to Claude (halt)Prompt hooks return JSON: `{decision: approve|block|ask}`## stdin/stdout ContractInput JSON includes `tool_name`, `tool_input` (PreToolUse), `user_prompt` (UserPromptSubmit), etc.Output JSON:```json{"continue": true, "systemMessage": "..."}```## Example: Write Validation```json{ "PreToolUse": [{ "matcher": "Write|Edit", "hooks": [{"type": "command", "command": "bash ${CLAUDE_PLUGIN_ROOT}/hooks/validate.sh"}] }]}```Script:```bash#!/bin/bashinput=$(cat)file=$(echo "$input" | jq -r '.tool_input.file_path')[[ "$file" == *".."* ]] && echo '{"decision":"deny"}' >&2 && exit 2[[ "$file" == *".env"* ]] && echo '{"decision":"deny"}' >&2 && exit 2echo '{"decision":"approve"}'```## Critical Rules- Quote all bash variables: `"$var"` not `$var`- Use `${CLAUDE_PLUGIN_ROOT}` for portability- Set timeouts: command 60s, prompt 30s- Validate all inputs- Hooks load at session start — restart to apply changes---**See REFERENCE.md for:** full event catalog, matcher patterns, testing, environment variables.

Frequently asked questions