Hook Creator

What it does

When your agent uses it

• The user wants to
• Create a new hook
• Configure automatic formatting
• Add file protection

Example prompts

• “/hook-creator”

Requirements

• Python 3
• Node.js

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

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

What it can do on your machine

Read from SKILL.md and the folder at commit 172bdd4. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • jq
  • npx
  • python3

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use npx, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Hook Creator loads about 662 tokens when it runs, and up to ~3k if it reads all its reference files. Until then it costs about 92 tokens; SKILL.md has 186 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~92

When it runs · the whole SKILL.md, loaded when a task matches

~662

With references · SKILL.md plus every file in references/, read only if the agent opens them

~3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NoteMentions a .env fileSKILL.md:80

  **Block edits to .env files:**

• NoteMentions a .env fileSKILL.md:82

  ,{}).get('file_path',''); sys.exit(2 if '.env' in p else 0)"

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from greatSumini/cc-system at commit 172bdd4, republished under its MIT licence (© greatSumini). 186 words, ~662 tokens.

name

hook-creator

description

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.

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

# 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'

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

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

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)"

© greatSumini, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (references) in .claude/skills/hook-creator of greatSumini/cc-system.

• SKILL.md
• references/examples.md
• references/hook-events.md

Open the folder on GitHubat commit 172bdd4