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skarn

skarn is a plugin for Gemini CLI from skarn-security/agent-guard. Its token cost is not measured, scanned A, original, MIT.

A local security scanner for Gemini CLI sessions and the tools they load. It looks for exposed credentials, checks hooks and MCP servers, and reports risky tool calls with findings hidden.

In plain words
What is it for?
It is for scanning agent sessions, reviewing loaded hooks and MCP servers, and guarding tool execution.
Why use it?
It helps catch secrets accidentally shared in sessions and unsafe tools before they run.

Plugin for Gemini CLI

Written for Gemini CLI: a Gemini CLI extension manifest. Also seen: mentions Gemini CLI.

not rated 36repo changed 12d ago A scan tokens not measured original MIT

Good fit It is for scanning agent sessions, reviewing loaded hooks and MCP servers, and guarding tool execution.

Compare 6 plugins from other repositories ↓
Install with agentmods
npx agentmods add plugins/skarn-security/agent-guard/gemini-extension
View source ↗ skarn-security/agent-guard getskarn.com
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/skarn-security/agent-guard

Made for: Gemini CLI.

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 skarn

README.md
[![agentmods](https://agentmods.dev/badge/plugins/skarn-security/agent-guard/gemini-extension/github.svg)](https://agentmods.dev/plugins/skarn-security/agent-guard/gemini-extension)
Your own site
<a href="https://agentmods.dev/plugins/skarn-security/agent-guard/gemini-extension"><img src="https://agentmods.dev/badge/plugins/skarn-security/agent-guard/gemini-extension/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for skarn

Your own site · 80×15
<a href="https://agentmods.dev/plugins/skarn-security/agent-guard/gemini-extension"><img src="https://agentmods.dev/badge/plugins/skarn-security/agent-guard/gemini-extension.svg" alt="Reviewed on agentmods" width="80" 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

skarn 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 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

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.

gemini-extension.json · 15 lines

What it actually says

{
  "name": "skarn",
  "description": "Security scanner for Gemini CLI: finds leaked credentials and secrets in your sessions, vets the hooks and MCP servers the CLI loads, and runs a pre-execution guard that reports the tool calls it would have flagged. Everything runs locally on the Skarn engine and every finding comes back redacted.",
  "mcpServers": {
    "skarn": {
      "command": "skarn",
      "args": [
        "mcp"
      ]
    }
  },
  "contextFileName": "GEMINI.md",
  "version": "0.33.0"
}
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. 12d ago Changed d277787bc738
  2. 22d ago Changed 20727f8edccf
  3. 1mo ago Changed ca6761fcc356
  4. 1mo ago Changed ab3ce7979ac1
  5. 1mo ago First seen · 15 lines scan A 56269ec4afbc

Subscribe to this mod's changes

skarn is a plugin published in the GitHub repository skarn-security/agent-guard (36 stars, last pushed 13d ago), licensed MIT. Its token cost is not measured: this kind of file is read by the harness, not the model. 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 2026-09-10.

Securitygemini-cli-extension
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