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PreToolUse

PreToolUse is a hook for Claude Code from jscott3201/ai-agent-skills. Its token cost is not measured, scanned C, original, no licence file.

A check that runs before an agent uses Bash, the command-line shell, and examines the planned shell commands.

In plain words
What is it for?
Use it to apply a pre-command check to Bash tool calls.
Why use it?
It can catch issues before commands run, including cases involving the five commands covered by the inline check.

Hook for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the justin-tools plugin — 26 skills, 9 agents, 4 hooks shipped together

One of 4 entries in hooks.json upstream. Installing this one merges just its entry into your config; the other 3 are separate, each on its own page.

not rated 2repo 5mo ago C scan tokens not measured no licence

Good fit Use it to apply a pre-command check to Bash tool calls.

Compare 6 hooks from other repositories ↓
Install with agentmods
npx agentmods add hooks/jscott3201/ai-agent-skills/pre-tool-use
View source ↗ jscott3201/ai-agent-skills
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.

Clone the repo
git clone --depth 1 https://github.com/jscott3201/ai-agent-skills

Made for: Claude Code.

Or install justin-tools, the plugin that ships this one along with the rest of its 26 skills, 9 agents, 4 hooks.

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/jscott3201/ai-agent-skills/pre-tool-use/github.svg)](https://agentmods.dev/hooks/jscott3201/ai-agent-skills/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/jscott3201/ai-agent-skills/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/jscott3201/ai-agent-skills/pre-tool-use/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for PreToolUse

Your own site · 80×15
<a href="https://agentmods.dev/hooks/jscott3201/ai-agent-skills/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/jscott3201/ai-agent-skills/pre-tool-use.svg" alt="Reviewed on agentmods" width="80" 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 C 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown No closer match found in the catalogue.
Security

Grade C, and why

PreToolUse scanned grade C with 1 finding 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 9d 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

"if": "Bash(rm -rf *)",
hooks/hooks.json · 34 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Same file

What else hooks.json configures

This page is one entry in a file that holds 4. 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. 9d ago First seen · 34 lines scan C 183bdc639fc3

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository jscott3201/ai-agent-skills (2 stars, last pushed 5mo ago), with no licence file. Its token cost is not measured: a hook is shell that never enters the context. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Related

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SessionStart

Runs when a session starts, executing on-start.js via node. From google-gemini/gemini-cli.

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PreToolUse

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PreToolUse

Runs before the agent uses a tool, executing pre-write.sh and pre-bash.sh (2 commands). From anthropics/claude-cookbooks.

anthropics/claude-cookbooks · not measured

PostToolUse

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