PreToolUse

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

A pre-tool-use hook that runs a check before Bash commands are executed, including a safeguard around merging GitHub pull requests.

In plain words
What is it for?
Use it in a Claude-style agent setup to run the project’s arm-base check before shell commands and to fail closed for uncertain release pull-request merges.
Why use it?
It can block a risky merge when the project’s release-branch check is unavailable or cannot prove that the merge is safe.

Hook for Claude Code

Written for Claude Code: $CLAUDE_PROJECT_DIR variable.

Part of the sparq plugin — 55 skills, 20 agents, 2 hooks shipped together

One of 3 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/sparq-org/sparq/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/sparq-org/sparq

Made for: Claude Code.

Or install sparq, the plugin that ships this one along with the rest of its 55 skills, 20 agents, 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/sparq-org/sparq/pre-tool-use.svg)](https://agentmods.dev/hooks/sparq-org/sparq/pre-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/sparq-org/sparq/pre-tool-use"><img src="https://agentmods.dev/badge/hooks/sparq-org/sparq/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 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.

.claude/settings.json · 23 lines

How it starts

The opening of the file, as written. The whole thing — 23 lines — stays where its author put it; the contents beside it link to each section on GitHub.

{
  "PreToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "hook_input=$(cat); guard=\"$CLAUDE_PROJECT_DIR/scripts/check-pr-arm-base.py\"; if [ -n \"$CLAUDE_PROJECT_DIR\" ] && [ -r \"$guard\" ] && guard_output=$(printf '%s' \"$hook_input\" | python3 \"$guard\") && [ -n \"$guard_output\" ]; then printf '%s\\n' \"$guard_output\"; elif printf '%s' \"$hook_input\" | grep -Eq 'gh[[:space:]]+pr[[:space:]]+merge'; then printf '%s\\n' '{\"hookSpecificOutput\":{\"hookEventName\":\"PreToolUse\",\"permissionDecision\":\"deny\",\"permissionDecisionReason\":\"🤖 SPARQ arm guard: scripts/check-pr-arm-base.py could not run, so this gh pr merge cannot be proven not to be the release-plz Release PR. DENYING (fail-closed, #1135 - a crates.io version can never be unpublished). Restore the guard script, or have a maintainer merge by hand.\"}}'; else printf '%s\\n' '{\"hookSpecificOutput\":{\"hookEventName\":\"PreToolUse\",\"permissionDecision\":\"allow\",\"permissionDecisionReason\":\"🤖 SPARQ arm guard: guard script unavailable or failed and this is not a gh pr merge, so no arm is being gated; allowing (the stacked-base axis is fail-open by design).\"}}'; fi",
          "timeout": 40,
          "statusMessage": "Stacked-PR arm guard: checking PR base is main…"
        },
        {
          "type": "agent",
          "agent": "sparq-perf-reviewer",
          "model": "claude-opus-5",
          "timeout": 300,
          "statusMessage": "PERFORMANCE-discretion gate: reviewing PR before arm…",
          "prompt": "You are the sparq PERFORMANCE-discretion gate (the sparq-perf-reviewer agent). This is a PreToolUse hook on Bash. The tool call being gated is:\n\n$ARGUMENTS\n\nFIRST: inspect tool_input.command. If it is NOT a PR-arming command — i.e. it is NOT a `gh pr merge` that arms a PR for the merge train (look for `gh pr merge` with `--auto`) — then this is out of your scope: immediately ALLOW it untouched. Return exa

Read the full file on GitHub · 23 lines

Same file

What else settings.json configures

This page is one entry in a file that holds 3. 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 · 23 lines scan A 99e9e797ca4b

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository sparq-org/sparq (10 stars, last pushed today), 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.