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PreToolUse

PreToolUse is a hook for Claude Code from hzeng-otterai/ai-course-example. Its token cost is not measured, scanned A, original, Apache-2.0.

A pre-action safety check that runs before an agent uses a Bash command, a way to execute shell commands. The example checks whether a command would delete a file named db.sqlite3 and can stop it.

In plain words
What is it for?
Use it as a hook that reviews Bash commands before execution and blocks commands matching a rule, such as deleting db.sqlite3.
Why use it?
It adds an automatic guard against a specific destructive command reaching the shell. This can protect a development database from accidental deletion.

Hook for Claude Code

Written for Claude Code: PreToolUse hook event.

One of 2 entries in settings.json upstream. Installing this one merges just its entry into your config; the other 1 are separate, each on its own page.

not rated 11repo 4mo ago A scan tokens not measured original Apache-2.0

Good fit Use it as a hook that reviews Bash commands before execution and blocks commands matching a rule, such as deleting db.sqlite3.

Compare 6 hooks from other repositories ↓
Install with agentmods
npx agentmods add hooks/hzeng-otterai/ai-course-example/pre-tool-use
View source ↗ hzeng-otterai/ai-course-example
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/hzeng-otterai/ai-course-example

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/hzeng-otterai/ai-course-example/pre-tool-use.svg)](https://agentmods.dev/hooks/hzeng-otterai/ai-course-example/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/hzeng-otterai/ai-course-example/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/hzeng-otterai/ai-course-example/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. A grade says what 26 rules found in the file — not that it is safe.
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 7d 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.

notebook_app_by_cc/.claude/settings.json · 14 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "jq -r '.tool_input.command' | grep -qE '(rm|unlink|shred|del).*db\\.sqlite3' && echo '{\"continue\": false, \"stopReason\": \"Deleting db.sqlite3 is not allowed. This would destroy the development database.\"}' || true",
          "statusMessage": "Checking for db.sqlite3 deletion..."
        }
      ]
    }
  ]
}
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. 7d ago First seen · 14 lines scan A d048cc135ebf

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository hzeng-otterai/ai-course-example (11 stars, last pushed 4mo ago), licensed Apache-2.0. 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.

Security
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.

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PreCompact

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