PreToolUse

PreToolUse is a hook for Claude Code from MokeyBytes/claude-baseline. Its token cost is not measured, scanned A, original, MIT.

A set of automatic checks that runs before the agent uses Bash, file-editing tools, notebook editing, or other agents. These checks validate commands, guard file changes, and guard agent calls.

In plain words
What is it for?
Use it to validate Bash commands, inspect or restrict file-writing actions, and check Agent tool calls before they run. The exact rules are defined in validate-bash.sh, guard-files.sh, and guard-agents.sh.
Why use it?
It adds checks before potentially risky tools are used, helping enforce project rules around commands, file edits, and delegated work.

Hook for Claude Code

One of 7 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/mokeybytes/claude-baseline/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/MokeyBytes/claude-baseline

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/mokeybytes/claude-baseline/pre-tool-use.svg)](https://agentmods.dev/hooks/mokeybytes/claude-baseline/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/mokeybytes/claude-baseline/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/mokeybytes/claude-baseline/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 3d 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 · 34 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/validate-bash.sh",
          "timeout": 30
        }
      ]
    },
    {
      "matcher": "Write|Edit|NotebookEdit",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/guard-files.sh",
          "timeout": 30
        }
      ]
    },
    {
      "matcher": "Agent",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/guard-agents.sh",
          "timeout": 10
        }
      ]
    }
  ]
}
Same file

What else settings.json configures

This page is one entry in a file that holds 7. 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. 3d ago First seen · 34 lines scan A 3706bebb9169

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository MokeyBytes/claude-baseline (2 stars, last pushed 5d ago), 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 2026-08-31.