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PreToolUse

PreToolUse is a hook for Claude Code from dbwls99706/ros2-engineering-skills. Its token cost is not measured, scanned A, original, Apache-2.0.

A pre-action check that runs a Python validation script before an agent edits files, writes files, combines edits, or runs shell commands.

In plain words
What is it for?
Use it as a hook for Edit, Write, MultiEdit, and Bash actions in agent workflows.
Why use it?
It can catch problems before those tool actions change the project.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the ros2-engineering plugin — 1 skill, 2 hooks shipped together

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

not rated 163repo +4 today A scan tokens not measured original Apache-2.0

Good fit Use it as a hook for Edit, Write, MultiEdit, and Bash actions in agent workflows.

Compare 6 hooks from other repositories ↓
View source ↗ dbwls99706/ros2-engineering-skills
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add dbwls99706/ros2-engineering-skills
Claude Code
/plugin install ros2-engineering

Made for: Claude Code.

Or install ros2-engineering, the plugin that ships this one along with the rest of its 1 skill, 2 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/dbwls99706/ros2-engineering-skills/pre-tool-use.svg)](https://agentmods.dev/hooks/dbwls99706/ros2-engineering-skills/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/dbwls99706/ros2-engineering-skills/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/dbwls99706/ros2-engineering-skills/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 8d 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.

hooks/hooks.json · 14 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Edit|Write|MultiEdit|Bash",
      "hooks": [
        {
          "type": "command",
          "command": "python3 \"${CLAUDE_PLUGIN_ROOT}/scripts/skill_validate_hook.py\"",
          "timeout": 10
        }
      ]
    }
  ]
}
Same file

What else hooks.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. 8d ago First seen · 14 lines scan A 70b08938ce83

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository dbwls99706/ros2-engineering-skills (163 stars, last pushed today), 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.

Claude CodeSecurityagent-skillclauderoboticsros2
Related

Other hooks, from other repositories

PostToolUse

Runs after a tool call finishes for Write and Edit tool calls, executing format_and_lint.sh. From supabase/supabase.

supabase/supabase · not measured

SessionStart

Runs when a session starts on startup, executing install_pkgs.sh. From supabase/supabase.

supabase/supabase · not measured

SessionStart

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

google-gemini/gemini-cli · not measured

PreToolUse

Runs before the agent uses a tool for Bash tool calls, running an inline shell check. From apache/superset.

apache/superset · not measured

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

PreCompact

Runs before the context is compacted for manual and auto tool calls, executing hook-handler.cjs via node (4 commands). From ruvnet/RuView.

ruvnet/RuView · not measured