PreToolUse

PreToolUse is a hook for Claude Code from Totoro-jam/battle-tested-patterns. Its token cost is not measured, scanned A, original, MIT.

A pre-tool hook that checks Bash commands before the coding agent runs them.

In plain words
What is it for?
Preventing commands such as forceful resets, forced cleanup, branch deletion, or pushing changes from running automatically.
Why use it?
It blocks several destructive Git commands, reducing the risk of accidentally deleting work or changing shared repository history.

Hook for Claude Code

Written for Claude Code: PreToolUse hook event.

One of 2 entries in settings.json — they are configured in one file and arrive together.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add hooks/totoro-jam/battle-tested-patterns/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/Totoro-jam/battle-tested-patterns

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for PreToolUse

README.md
[![agentmods](https://agentmods.dev/badge/hooks/totoro-jam/battle-tested-patterns/pre-tool-use.svg)](https://agentmods.dev/hooks/totoro-jam/battle-tested-patterns/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/totoro-jam/battle-tested-patterns/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/totoro-jam/battle-tested-patterns/pre-tool-use.svg" alt="Measured on agentmods" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured Not applicable: nothing here is loaded into a session.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

PreToolUse scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

A static scan of the commands this hook runs, not an audit. A hook is shell that executes on your machine at the event it names, which is why every command in it is printed with what was found.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/settings.json · 13 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "bash -c 'CMD=\"$CLAUDE_TOOL_INPUT\"; if echo \"$CMD\" | grep -qE \"git push|git reset --hard|git clean -f|git branch -D\"; then echo \"BLOCKED: Destructive git operation not allowed. Commit only, push manually.\" >&2; exit 2; fi'"
        }
      ]
    }
  ]
}
Same file

What else settings.json configures

This page is one entry in a file that holds 2. Installing the file brings all of them; each is measured and scanned on its own page.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 13 lines scan A 89bb2f83c759

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository Totoro-jam/battle-tested-patterns (340 stars, last pushed yesterday), licensed MIT. Its token cost is not measured: a hook is shell that never enters the context. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.