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PostToolUse

PostToolUse is a hook for Claude Code from JuanMarchetto/agent-skills. Its token cost is not measured, scanned A, original, MIT.

A post-tool hook that checks Bash command results for errors and runs a detection script.

In plain words
What is it for?
Use it to monitor Bash commands after they finish and trigger error handling when a command fails.
Why use it?
It catches failed shell commands automatically so they can be reviewed and turned into lessons.

Hook for Claude Code

Written for Claude Code: PostToolUse hook event.

Part of the learn-by-mistake plugin — 1 skill, 4 commands, 3 hooks shipped together

One of 3 entries in hooks.json upstream. Installing this one merges just its entry into your config; the other 2 are separate, each on its own page.

not rated 5repo 5mo ago A scan tokens not measured original MIT

Good fit Use it to monitor Bash commands after they finish and trigger error handling when a command fails.

Compare 6 hooks from other repositories ↓
Install with agentmods
npx agentmods add hooks/juanmarchetto/agent-skills/post-tool-use
View source ↗ JuanMarchetto/agent-skills
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.

Clone the repo
git clone --depth 1 https://github.com/JuanMarchetto/agent-skills

Made for: Claude Code.

Or install learn-by-mistake, the plugin that ships this one along with the rest of its 1 skill, 4 commands, 3 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 PostToolUse

README.md
[![agentmods](https://agentmods.dev/badge/hooks/juanmarchetto/agent-skills/post-tool-use.svg)](https://agentmods.dev/hooks/juanmarchetto/agent-skills/post-tool-use)
Your own site
<a href="https://agentmods.dev/hooks/juanmarchetto/agent-skills/post-tool-use"><img src="https://agentmods.dev/badge/hooks/juanmarchetto/agent-skills/post-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

PostToolUse 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 4d 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.

skills/learn-by-mistake/hooks/hooks.json · 14 lines

What it actually says

{
  "PostToolUse": [
    {
      "matcher": "Bash",
      "hooks": [
        {
          "type": "command",
          "command": "bash hooks/scripts/detect-error.sh",
          "timeout": 5
        }
      ]
    }
  ]
}
Same file

What else hooks.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. 4d ago First seen · 14 lines scan A 794f30c26318

Subscribe to this mod's changes

PostToolUse is a hook published in the GitHub repository JuanMarchetto/agent-skills (5 stars, last pushed 5mo 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 2026-09-03.

Claude CodeDebuggingEvaluationai-agentsai-toolsautomationbrowser-automation
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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.

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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