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 fellipeutaka/leon --skill web-design-guidelinesgit clone --depth 1 https://github.com/fellipeutaka/leonWrote 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/fellipeutaka/leon/web-design-guidelines)<a href="https://agentmods.dev/skills/fellipeutaka/leon/web-design-guidelines"><img src="https://agentmods.dev/badge/skills/fellipeutaka/leon/web-design-guidelines.svg" alt="Measured on agentmods" 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 | $0.00044 | $0.00268 |
| Opus 5 | $0.00022 | $0.00134 |
| Sonnet 5 | $0.00009 | $0.00054 |
| Haiku 4.5 | $0.00004 | $0.00027 |
Grade A, and why
web-design-guidelines 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 3d 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.
This is a copy
100% identical to web-design-guidelines — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
What it actually says
Web Interface Guidelines
Review files for compliance with Web Interface Guidelines.
How It Works
- Fetch the latest guidelines from the source URL below
- Read the specified files (or prompt user for files/pattern)
- Check against all rules in the fetched guidelines
- Output findings in the terse
file:lineformat
Guidelines Source
Fetch fresh guidelines before each review:
https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md
Use WebFetch to retrieve the latest rules. The fetched content contains all the rules and output format instructions.
Usage
When a user provides a file or pattern argument:
- Fetch guidelines from the source URL above
- Read the specified files
- Apply all rules from the fetched guidelines
- Output findings using the format specified in the guidelines
If no files specified, ask the user which files to review.
What ships with it
1 file 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.
- 3d ago First seen · 40 lines · 44 tokens per session scan A f4647ca866a3
web-design-guidelines is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed 3d ago), licensed MIT. It adds 44 tokens to every session and 268 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to web-design-guidelines, differing in 0 lines, and is treated as a copy.
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