PreToolUse

A set of checks that run before an agent uses selected tools, such as editing files, running commands, or reading project data.

In plain words
What is it for?
Use it to enforce project rules before tool calls, block unsafe file changes, check translation strings and stories, and prevent broken specification-to-plan workflows.
Why use it?
It can stop risky or disallowed changes before they happen, including edits to secrets, lockfiles, configuration, or required project files.

Hook for Claude Code

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/gaia-react/gaia/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/gaia-react/gaia

Made for: Claude Code.

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. Scan, not verified.
Origin original 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 2d 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.

"statusMessage": "Checking rm -rf safety…"
.claude/settings.json · 186 lines

How it starts

The opening of the file, as written. The whole thing — 186 lines — stays where its author put it; the contents beside it link to each section on GitHub.

{
  "PreToolUse": [
    {
      "matcher": "Skill",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/block-spec-plan-chain.sh",
          "statusMessage": "Checking spec→plan chain guard…"
        }
      ]
    },
    {
      "matcher": "Edit|Write|MultiEdit",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/block-env-write.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-eslint-config-edit.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-lockfile-edit.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-secrets-write.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-vitest-globals-tsconfig.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/check-i18n-strings.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/check-story-exists.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-manifest-write.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-selfheal-paths.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-worktree-path-mismatch.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-invalid-yaml-write.sh"
        }
      ]
    },
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": ".claude/hooks/block-bare-test.sh"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-main-destructive-git.sh",
          "statusMessage": "Checking main-branch protection…"
        },
        {
          "type": "command",
          "command": ".claude/hooks/block-no-verify.sh",

Read the full file on GitHub · 186 lines

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. 2d ago First seen · 186 lines scan C e919a036cad2

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository gaia-react/gaia (22 stars, last pushed 2d ago), licensed MIT. 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 2026-08-30.