Agent skill

hook-template

Generate hook script from template

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/hook-template

SKILL.md

Hook Template Generator

Generate a hook script and configuration based on requirements.

Usage: /hook-template [hook-type] [purpose]

Hook Types

Type When it Runs Use Case
PreToolUse Before a tool runs Block, validate, add context
PostToolUse After a tool completes Log, notify, react
UserPromptSubmit User submits a prompt Context injection, validation
Stop Main agent stopping Completeness check, continue loops
SubagentStop Subagent finishes Task validation
SessionStart Session begins Context loading, env setup
SessionEnd Session ends Cleanup, logging
PreCompact Before context compaction Preserve critical context
PostCompact After compaction completes Context recovery
Notification User is notified External alerts (Slack, etc.)
Elicitation MCP server requests input Override elicitation
ElicitationResult Elicitation result available Post-process

Hook Config Fields

Field Type Required Default Notes
type String Yes - "command" or "prompt"
command String If type=command - Shell command to execute
prompt String If type=prompt - Natural language prompt for LLM
timeout Integer No 60s (command), 30s (prompt) Seconds
once Boolean No false Run hook only once per session

Hook Input (stdin JSON)

All hooks receive JSON on stdin with these fields:

json
{
  "session_id": "abc123",
  "transcript_path": "/path/to/transcript.txt",
  "cwd": "/current/working/dir",
  "permission_mode": "ask",
  "hook_event_name": "PreToolUse",
  "tool_name": "Write",
  "tool_input": { "file_path": "/path/to/file" }
}

Process

  1. Gather Requirements

    • Hook type
    • Purpose
    • Matcher (for Pre/PostToolUse: tool name, regex, or *)

  2. Generate Script at .claude/hooks/[name].sh

  3. Update settings.json with hook config

  4. Make Executable: chmod +x

  5. Validate with /hooks-check

Templates

PreToolUse (Blocker)

bash
#!/bin/bash
INPUT=$(cat)
TOOL=$(echo "$INPUT" | jq -r '.tool_name')
FILE=$(echo "$INPUT" | jq -r '.tool_input.file_path // empty')

# Block edits to specific files
if [[ "$FILE" == *"package-lock.json"* ]]; then
    echo "BLOCKED: Do not edit lockfiles directly" >&2
    exit 2
fi
exit 0  # Allow (no output needed)

PreToolUse (Context Adding)

bash
#!/bin/bash
cat > /dev/null  # Consume stdin
INFO="This file requires careful review"
jq -n --arg ctx "$INFO" '{
    "hookSpecificOutput": {
        "hookEventName": "PreToolUse",
        "additionalContext": $ctx
    }
}'
exit 0

PostToolUse (Logger)

bash
#!/bin/bash
INPUT=$(cat)
# Process and log... (no stdout needed)
exit 0

Stop (Auto-Loop)

bash
#!/bin/bash
CHECKPOINT=".auto-loop/checkpoint.json"
if [[ ! -f "$CHECKPOINT" ]]; then
    exit 0  # Allow stop
fi
# Block stop to continue loop
jq -n --arg reason "Continuing iteration" \
    '{"decision": "block", "reason": $reason}'
exit 0

SessionStart (Context Load)

bash
#!/bin/bash
cat > /dev/null
echo "Loading project context..." >&2
exit 0

Prompt Hook (LLM-based)

Instead of a bash script, use type: "prompt" in settings.json:

json
{
  "hooks": {
    "Stop": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "prompt",
            "prompt": "Review the work done. Return 'approve' if complete, or 'block' with reason.",
            "timeout": 30
          }
        ]
      }
    ]
  }
}

Settings.json Format

json
{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/validate.sh",
            "timeout": 60
          }
        ]
      }
    ],
    "SessionStart": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/load-context.sh",
            "once": true
          }
        ]
      }
    ]
  }
}

Example

/hook-template PreToolUse "block edits to package-lock.json"

Creates:
- .claude/hooks/protect-lockfile.sh
- Updates .claude/settings.json

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