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 agentmods add skills/devantler-tech/agent-plugins/web-design-guidelinesnpx skills add devantler-tech/agent-plugins --skill web-design-guidelinesgit clone --depth 1 https://github.com/devantler-tech/agent-pluginsWhat 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 | $0.00044 | $0.00339 |
| Opus 5 | $0.00022 | $0.00169 |
| Sonnet 5 | $0.00009 | $0.00068 |
| Haiku 4.5 | $0.00004 | $0.00034 |
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 yesterday.
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
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 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.
- yesterday First seen · 43 lines · 44 tokens per session scan A 4b359aa759cd
web-design-guidelines is a skill published in the GitHub repository devantler-tech/agent-plugins (2 stars, last pushed yesterday), licensed Apache-2.0. It adds 44 tokens to every session and 339 once invoked, about $0.0002 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 2026-08-31.
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