PreToolUse

PreToolUse is a hook for Claude Code from VasiHemanth/tokentelemetry. Its token cost is not measured, scanned A, a copy of SessionStart, MIT.

A set of checks that runs automatically before an agent uses shell commands or changes files. The listed checks enforce JSON updates, review certain code changes, and protect sensitive files.

In plain words
What is it for?
Use it in an agent project to run checks before Bash, Write, Edit, MultiEdit, or NotebookEdit actions.
Why use it?
It catches policy or safety issues before tool actions happen. This reduces the chance of unreviewed changes or accidental edits to protected files.

Hook for Claude Code

One of 2 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/vasihemanth/tokentelemetry/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/VasiHemanth/tokentelemetry

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/vasihemanth/tokentelemetry/pre-tool-use.svg)](https://agentmods.dev/hooks/vasihemanth/tokentelemetry/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/vasihemanth/tokentelemetry/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/vasihemanth/tokentelemetry/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 50% copy Near-identical to another mod 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 6d 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.

Origin

This is a copy

50% identical to SessionStart — 21 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/settings.json · 26 lines

What it actually says

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "${CLAUDE_PROJECT_DIR}/.claude/hooks/enforce-update-json.py"
        },
        {
          "type": "command",
          "command": "${CLAUDE_PROJECT_DIR}/.claude/hooks/prepush-claude-review.py"
        }
      ]
    },
    {
      "matcher": "Write|Edit|MultiEdit|NotebookEdit",
      "hooks": [
        {
          "type": "command",
          "command": "${CLAUDE_PROJECT_DIR}/.claude/hooks/protect-sensitive-files.py"
        }
      ]
    }
  ]
}
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. 6d ago First seen · 26 lines scan A 5ed5b11b94d3

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository VasiHemanth/tokentelemetry (342 stars, last pushed yesterday), 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. It is 50% identical to SessionStart, differing in 21 lines, and is treated as a copy.