A safety check that runs before a coding tool is called. It checks the call against the current turn’s certificate and checks where its arguments came from.

Use it to place provenance and authorization checks in front of tool calls in a Gemini harness.

It can catch tool calls whose authorization or input history does not match the current turn. This adds a check before the call is executed.

BeforeTool — Hook by ilyautov

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/ilyautov/cordon/before-tool

Clone the repo

git clone --depth 1 https://github.com/ilyautov/cordon

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

BeforeTool 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 yesterday.

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.

hooks/hooks.json · 15 lines

What it actually says

{
  "BeforeTool": [
    {
      "hooks": [
        {
          "type": "command",
          "name": "cordon",
          "description": "Checks the call against the turn's certificate and the provenance of its arguments",
          "command": "node \"${extensionPath}${/}plugin${/}dist${/}cli.js\" hook --harness gemini",
          "timeout": 10000
        }
      ]
    }
  ]
}

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.

yesterday First seen · 15 lines scan A 37e9354afa87

Subscribe to this mod's changes

BeforeTool is a hook published in the GitHub repository ilyautov/cordon (1 stars, last pushed 11d 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 2026-08-31.

Data and AI Security agent-security ai-security claude-code gemini-cli llm-security mcp

BeforeTool

Getting it into your agent

Grade A, and why

Nothing flagged

What it actually says

What this file has done since we first saw it

Other hooks, from other repositories

PreToolUse

PreToolUse

PostToolUse

Notification

SessionEnd

UserPromptSubmit