Borrowing it
Nothing to install: this file belongs to skarn-security/agent-guard. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/skarn-security/agent-guard/main/GEMINI.mdgit clone --depth 1 https://github.com/skarn-security/agent-guardWrote 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.
[](https://agentmods.dev/instructions/skarn-security/agent-guard/gemini-md)<a href="https://agentmods.dev/instructions/skarn-security/agent-guard/gemini-md"><img src="https://agentmods.dev/badge/instructions/skarn-security/agent-guard/gemini-md/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.
<a href="https://agentmods.dev/instructions/skarn-security/agent-guard/gemini-md"><img src="https://agentmods.dev/badge/instructions/skarn-security/agent-guard/gemini-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00373 | $0.00373 |
| Opus 5.5 | $0.00149 | $0.00149 |
| Sonnet 5.5 | $0.00075 | $0.00075 |
| Haiku 4.5 | $0.00037 | $0.00037 |
Grade A, and why
agent-guard GEMINI.md 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 1mo 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.
What it actually says
Skarn
This extension adds a local skarn MCP server and the skarn-audit skill. The server runs on the user's machine, makes no network call, and exposes four tools:
scan_sessionsreturns findings from past AI coding sessions. A detected credential value appears only in masked form; file paths, session ids, timestamps, and a Compliance API export's user and workspace ids come back unmasked.vet_configsreturns findings on the local assistant configuration. They quote excerpts of hook commands and MCP server definitions, with detected credential values masked.list_sessionsreturns session metadata:session_id,cli,user_id, the first and last timestamps, and message, call, and token counts. Never message content.session_statsreturns aggregate counts. Never message content.
Every tool is read-only. None of them writes a file, changes a configuration, or reaches the network.
A masked value is masked because it is a credential. Never reconstruct one, never infer the original from the surrounding text, and never ask the user to paste the unmasked value back. Report the finding by its rule, severity, and location instead.
Reach for the skarn-audit skill when the user asks whether a session or a configuration leaked something, or asks for an audit before sharing a repository or a transcript. This extension carries that skill only.
The guard hook in this extension runs in audit mode. It reports the verdict it would have reached and never blocks what the agent does.
If gemini mcp list shows the skarn server as Disconnected, run skarn --version in the same shell. command not found means the binary is not installed or is not on the PATH the CLI inherits. Install it as the repository README describes.
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.
- 1mo ago Changed · +53 tokens per session a046eceb4318
- 1mo ago First seen · 19 lines · 320 tokens per session scan A 58f13f02dab3
agent-guard GEMINI.md is an instructions file published in the GitHub repository skarn-security/agent-guard (37 stars, last pushed 23d ago), licensed MIT. It adds 373 tokens to every session, about $0.0015 per session on Opus 5.5. 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 2026-08-30.
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