hook-template - SKILL.md Agent Skill

name: hook-template description: Generate hook script from template user-invocable: true

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:

{
  "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

Gather Requirements
- Hook type
- Purpose
- Matcher (for Pre/PostToolUse: tool name, regex, or *)
Generate Script at .claude/hooks/[name].sh
Update settings.json with hook config
Make Executable: chmod +x
Validate with /hooks-check

Templates

PreToolUse (Blocker)

#!/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)

#!/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)

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

Stop (Auto-Loop)

#!/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)

#!/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:

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

Settings.json Format

{
  "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