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 olgasafonova/SkillCheck-Free --skill skill-checkgit clone --depth 1 https://github.com/olgasafonova/SkillCheck-FreeWrote 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/olgasafonova/skillcheck-free/skill-check)<a href="https://agentmods.dev/skills/olgasafonova/skillcheck-free/skill-check"><img src="https://agentmods.dev/badge/skills/olgasafonova/skillcheck-free/skill-check/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/olgasafonova/skillcheck-free/skill-check"><img src="https://agentmods.dev/badge/skills/olgasafonova/skillcheck-free/skill-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00092 | $0.04436 |
| Opus 5 | $0.00046 | $0.02218 |
| Sonnet 5 | $0.00018 | $0.00887 |
| Haiku 4.5 | $0.00009 | $0.00444 |
Grade A, and why
skill-check 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 8d 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.
How it starts
The opening of the file, as written. The whole thing — 353 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SkillCheck (Free)
Check skills against Anthropic guidelines and the agentskills specification. This file contains Free tier validation rules.
Want deeper analysis? Upgrade to Pro for anti-slop detection, security scanning, token optimization, WCAG compliance, enterprise checks, and Eval Kit (auto-generated test prompts for your skills).
Prerequisites
- Any AI assistant with file Read capability (Claude Code, Cursor, Windsurf, Codex CLI)
- Works on any platform (Unix/macOS/Windows)
- No special tools required (Read-only; the Invisible Unicode checks also use Grep, which stays read-only)
- No environment variables or API keys required; the checks run fully offline
Interface
- Input: path(s) to SKILL.md files, plus any
references/*.mdfiles in the same skill folder - Output: a validation report listing each issue with check ID, severity (Critical / Warning / Suggestion), line number, and fix; strengths reported in a separate list
- Modes: runs standalone on a single skill or over a directory of skills, one report per skill
Workflow
Run the four stages in order for each target skill. Data flows forward: the file list from Step 1 feeds Step 2, the loaded content feeds Step 3, and the findings feed Step 4.
- Step 1: Locate — find target SKILL.md file(s) with Glob
- Step 2: Read — load the SKILL.md content and any
references/files - Step 3: Validate — apply each rule section below to the loaded content
- Step 4: Report — list issues found with severity, line number, and fix
Execution limits: maximum iterations: 1 validation pass per skill. Stop after every located skill has been reported once; abort if a SKILL.md cannot be read and say so in the report. The check is read-only and idempotent — safe to re-run, and repeated runs on unchanged files produce identical reports.
Free Tier Validation Rules
Worked valid/invalid examples for every check below are in references/examples.md. The rules are here; the examples are one file away to keep this file scannable.
What ships with it
4 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.
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.
- 8d ago Changed · +34 lines 5d7939476f6d
- 12d ago First seen · 319 lines · 92 tokens per session scan A d76c5a573c2c
skill-check is a skill published in the GitHub repository olgasafonova/SkillCheck-Free (37 stars, last pushed 12d ago), licensed MIT. It adds 92 tokens to every session and 4,436 once invoked, about $0.0005 per session on Opus 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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