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.
npx skills add simota/agent-skills --skill sentinelgit clone --depth 1 https://github.com/simota/agent-skillsWrote 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/skills/simota/agent-skills/sentinel)<a href="https://agentmods.dev/skills/simota/agent-skills/sentinel"><img src="https://agentmods.dev/badge/skills/simota/agent-skills/sentinel/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/skills/simota/agent-skills/sentinel"><img src="https://agentmods.dev/badge/skills/simota/agent-skills/sentinel.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 | $0.00043 | $0.05612 |
| Opus 5 | $0.00022 | $0.02806 |
| Sonnet 5 | $0.00009 | $0.01122 |
| Haiku 4.5 | $0.00004 | $0.00561 |
Grade C, and why
sentinel scanned grade C with 2 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 6d 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- CAPABILITIES_SUMMARY: - secret_detection: Hardcoded secrets, API keys, credentials (regex + entropy, 800+ secret types) - injection_prevention: SQL, XSS, command, prompt, NoSQL injection - input_validation: Audit in Reads MCP configurationlowAgent snooping
mcp.json carries server URLs and auth tokens; reading it lets a mod discover and abuse other integrations.
- Secret detection: regex + entropy + context-aware validation, at pre-commit **and** CI/CD. Include MCP configs (`.cursor/mcp.json`, `claude_desktop_config.json`, MCP-server `.env`) and Docker images/Dockerfiles (18% co Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
How it starts
The opening of the file, as written. The whole thing — 273 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Sentinel
Static security auditor. Identify and fix ONE security issue, or add ONE enhancement, per invocation.
What ships with it
16 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- _common 10 B
- reference/_common 13 B
- reference/ai-code-security.md 7.6 KB
- reference/ai-security.md 7.3 KB
- reference/api-security.md 6.6 KB
- reference/authn-audit.md 4.9 KB
- reference/authz-audit.md 5.5 KB
- reference/autorun-schema.md 1.7 KB
- reference/defensive-controls.md 7.6 KB
- reference/fix-prompt-generation.md 14 KB
- reference/judge 11 B
- reference/mobile-security.md 2.8 KB
- reference/owasp-2025-checklist.md 5.2 KB
- reference/supply-chain-security.md 15 KB
- reference/tri-engine-scan.md 17 KB
- reference/vulnerability-patterns.md 6.3 KB
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.
- 6d ago First seen · 273 lines · 43 tokens per session scan C fa6a394267a3
sentinel is a skill published in the GitHub repository simota/agent-skills (76 stars, last pushed 7d ago), licensed MIT. It adds 43 tokens to every session and 5,612 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 2 findings (hidden instructions, reads mcp configuration). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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