PreToolUse

A set of checks that runs before an agent uses file or command tools such as reading, editing, writing, searching, or running shell commands. It can also validate plans and changes before they are applied.

In plain words
What is it for?
Use it to run privacy checks before file or shell actions, validate plan updates, guard writes against an overall plan, and check that edits remain consistent with the plan.
Why use it?
It adds automatic checks around actions that may inspect or modify project files. This helps enforce privacy, planning, and consistency rules during an agent session.

Hook

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/evolplus/talos/pre-tool-use
Clone the repo
git clone --depth 1 https://github.com/evolplus/talos
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 78% 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 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.

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

78% identical to UserPromptSubmit — 245 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.

hooks/hooks.json · 266 lines

How it starts

The opening of the file, as written. The whole thing — 266 lines — stays where its author put it; the contents beside it link to each section on GitHub.

{
  "PreToolUse": [
    {
      "matcher": "Read|Edit|Write|MultiEdit|NotebookEdit|Bash|Glob|Grep",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/privacy-check.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/plan-update-validator.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write|Edit|MultiEdit|NotebookEdit",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/master-plan-write-guard.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write|Edit",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/plan-consistency-validator.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Task",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/kit-role-dispatch-guard.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/acceptance-scenarios-validator.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/self-containment-validator.cjs"
          ]
        }
      ]
    },
    {
      "matcher": "Write|Edit",
      "hooks": [
        {
          "type": "command",
          "command": "node",
          "args": [
            "${CLAUDE_PLUGIN_ROOT}/hooks/external

Read the full file on GitHub · 266 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 · 266 lines scan A ce8836c10493

Subscribe to this mod's changes

PreToolUse is a hook published in the GitHub repository evolplus/talos (8 stars, last pushed 28d ago), licensed Apache-2.0. 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 78% identical to UserPromptSubmit, differing in 245 lines, and is treated as a copy.