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 flitzrrr/frontend-design-skills --skill usabilitygit clone --depth 1 https://github.com/flitzrrr/frontend-design-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/flitzrrr/frontend-design-skills/usability)<a href="https://agentmods.dev/skills/flitzrrr/frontend-design-skills/usability"><img src="https://agentmods.dev/badge/skills/flitzrrr/frontend-design-skills/usability/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/flitzrrr/frontend-design-skills/usability"><img src="https://agentmods.dev/badge/skills/flitzrrr/frontend-design-skills/usability.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 | $0.00033 | $0.01445 |
| Opus 5.5 | $0.00013 | $0.00578 |
| Sonnet 5.5 | $0.00007 | $0.00289 |
| Haiku 4.5 | $0.00003 | $0.00145 |
Grade A, and why
usability 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.
How it starts
The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Usability
Usability is not a gut feeling — it is a measurable quality criterion. Every interaction must work without cognitive effort.
Scope
Use this skill when you:
- Evaluate a website or individual pages for usability
- Design or optimize forms
- Design error states and feedback mechanisms
- Conduct a heuristic evaluation based on Nielsen's heuristics
- Aim to increase conversion rates through improved usability
- Need to make content scannable and readable
Principles
1. Don't Make Me Think
Every interaction works without cognitive effort. Users don't read — they scan. Users don't choose optimally — they take the first available path.
2. Effectiveness Before Efficiency Before Satisfaction
The three ISO 9241 criteria build upon each other. First, the task must be achievable; then with minimal effort; then with satisfaction.
3. Conventions Beat Creativity
Users have learned patterns (logo top-left = homepage, search top-right, shopping cart icon). Only break these with demonstrable justification.
4. Aesthetic-Usability Effect
Aesthetically pleasing interfaces are perceived as more usable. Beauty is not a luxury — it is a usability factor.
5. Error Tolerance as a Requirement
Users make mistakes. Every interaction must be error-tolerant and provide clear feedback.
6. Measurability
Usability is measured through task completion, error rate, task time, and satisfaction scores.
Rules
DO: Enforce Consistency
- USE uniform fonts, colors, design elements, and writing conventions across all pages.
- ENSURE that similar page types have identical layouts.
- USE a consistent interaction model (same button styles, same hover effects, same form logic).
DO: Optimize Above the Fold
- PLACE the most important message, the primary CTA, and a clear headline in the visible area without scrolling.
- AVOID "Welcome" as the first headline. Use benefit-oriented statements instead.
DO: Keep Forms Minimal
- ASK only for required fields. Every additional field reduces the conversion rate.
- MARK required fields clearly.
- USE clear field labels — never use placeholders as the only labels.
- DISPLAY error messages directly at the affected field.
- PRESERVE correctly filled fields when errors occur.
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 First seen · 154 lines · 33 tokens per session scan A d526676c0d5a
usability is a skill published in the GitHub repository flitzrrr/frontend-design-skills (9 stars, last pushed 6mo ago), licensed MIT. It adds 33 tokens to every session and 1,445 once invoked, about $0.0001 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 2026-08-31.
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