hook-creator

greatSumini's avatarfrom greatSumini

Create and configure Claude Code hooks for customizing agent behavior. Use when the user wants to (1) create a new hook, (2) configure automatic formatting, logging, or notifications, (3) add file protection or custom permissions, (4) set up pre/post tool execution actions, or (5) asks about hook events like PreToolUse, PostToolUse, Notification, etc.

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[Developer Tools]

When & Why to Use This Skill

The Hook Creator skill empowers developers to customize and extend Claude Code's behavior through lifecycle hooks. By executing shell commands during events such as PreToolUse and PostToolUse, it enables automated code formatting, strict security guardrails, and comprehensive activity logging, making AI-assisted development more secure and efficient.

Use Cases

  • 1. Automated Code Quality: Automatically trigger linters or formatters (like Prettier or Ruff) immediately after the agent modifies a file to maintain style consistency.
  • 2. Security Guardrails: Define hooks to intercept and block the agent from reading or editing sensitive files such as .env, credentials, or private keys.
  • 3. Audit Logging & Observability: Create a persistent record of all shell commands executed by the agent to monitor behavior and facilitate debugging.
  • 4. Custom Notifications: Set up desktop alerts or Slack messages to notify the user when long-running tool executions or specific agent tasks are completed.
namehook-creator
descriptionCreate and configure Claude Code hooks for customizing agent behavior. Use when the user wants to (1) create a new hook, (2) configure automatic formatting, logging, or notifications, (3) add file protection or custom permissions, (4) set up pre/post tool execution actions, or (5) asks about hook events like PreToolUse, PostToolUse, Notification, etc.

Hook Creator

Create Claude Code hooks that execute shell commands at specific lifecycle events.

Hook Creation Workflow

  1. Identify the use case - Determine what the hook should accomplish
  2. Select the appropriate event - Choose from available hook events (see references/hook-events.md)
  3. Design the hook command - Write shell command that processes JSON input from stdin
  4. Configure the matcher - Set tool/event filter (use * for all, or specific tool names like Bash, Edit|Write)
  5. Choose storage location - User settings (~/.claude/settings.json) or project (.claude/settings.json)
  6. Test the hook - Verify behavior with a simple test case

Hook Configuration Structure

{
  "hooks": {
    "<EventName>": [
      {
        "matcher": "<ToolPattern>",
        "hooks": [
          {
            "type": "command",
            "command": "<shell-command>"
          }
        ]
      }
    ]
  }
}

Common Patterns

Reading Input Data

Hooks receive JSON via stdin. Use jq to extract fields:

# Extract tool input field
jq -r '.tool_input.file_path'

# Extract with fallback
jq -r '.tool_input.description // "No description"'

# Conditional processing
jq -r 'if .tool_input.file_path then .tool_input.file_path else empty end'

Exit Codes for PreToolUse

  • 0 - Allow the tool to proceed
  • 2 - Block the tool and provide feedback to Claude

Matcher Patterns

  • * - Match all tools
  • Bash - Match only Bash tool
  • Edit|Write - Match Edit or Write tools
  • Read - Match Read tool

Quick Examples

Log all bash commands:

jq -r '"\(.tool_input.command)"' >> ~/.claude/bash-log.txt

Auto-format TypeScript after edit:

jq -r '.tool_input.file_path' | { read f; [[ "$f" == *.ts ]] && npx prettier --write "$f"; }

Block edits to .env files:

python3 -c "import json,sys; p=json.load(sys.stdin).get('tool_input',{}).get('file_path',''); sys.exit(2 if '.env' in p else 0)"

Resources

  • Hook Events Reference: See references/hook-events.md for detailed event documentation with input/output schemas
  • Example Configurations: See references/examples.md for complete, tested hook configurations