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 helderberto/agent-skills --skill frontend-ui-engineeringgit clone --depth 1 https://github.com/helderberto/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/helderberto/agent-skills/frontend-ui-engineering)<a href="https://agentmods.dev/skills/helderberto/agent-skills/frontend-ui-engineering"><img src="https://agentmods.dev/badge/skills/helderberto/agent-skills/frontend-ui-engineering/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/helderberto/agent-skills/frontend-ui-engineering"><img src="https://agentmods.dev/badge/skills/helderberto/agent-skills/frontend-ui-engineering.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 | $0.00069 | $0.00674 |
| Opus 5.5 | $0.00028 | $0.00270 |
| Sonnet 5.5 | $0.00014 | $0.00135 |
| Haiku 4.5 | $0.00007 | $0.00067 |
Grade A, and why
frontend-ui-engineering 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 11d 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 — 36 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Frontend UI Engineering
Decide how to structure a UI unit before writing it, so the choices audits would catch late (accessibility, i18n, bundle cost, missing states) are made up front. Frontend counterpart to codebase-design: a component is a deep module — a lot of behaviour behind a small prop surface. This skill decides; tdd/build implement; the audit skills verify. Framework-agnostic.
1. Classify the unit
| Kind | Emphasis |
|---|---|
| Design-system primitive (Button, Input) | prop API, variants via props, tokens, a11y contract |
| Composite component | composition, state placement, required states |
| Page / route | data-fetching boundary, layout, loading/error at the route |
| Refactor of existing UI | shrink prop surface, extract states, remove magic values |
2. Decision pass — state each choice before coding
- Boundary & prop API. Smallest surface that serves callers. Prefer composition (
children/slots) over configuration. A growing set of boolean flags (isPrimary,isSmall,isLoading…) is a smell — three booleans is eight states, most untested; reach for avariant/sizeunion or composition. - Where state lives. The lowest owner that still works: local → lifted → server state → URL. No derived state stored twice; compute from source.
- Data & async. Decide the fetch boundary (route/loader vs. inside the component) and who owns caching. Keep rendering components separate from fetching ones where practical.
- Required UI states. Enumerate and design loading, empty, error, disabled (and partial/optimistic where relevant) now. Happy-path-only is unfinished.
- Styling. Design-system tokens, no magic colors/spacing. Variants through props, not one-off overrides.
- Responsive. Mobile-first; intentional breakpoints; no fixed widths that break small screens.
- Accessibility by construction. Semantic HTML first, ARIA last; keyboard + focus order; a label for every control; visible focus. Full WCAG pass belongs to
a11y-audit. - User-facing strings. Through the project's i18n path from the start. Coverage check belongs to
i18n.
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.
- 11d ago Changed · +1 lines d91ffe501583
- 14d ago Changed adbd4db9c3fd
- 1mo ago Changed · -14 tokens per session b6dd3c382962
- 1mo ago Changed · -55 lines · -19 tokens per session bb63956ccb03
- 1mo ago First seen · 90 lines · 102 tokens per session scan A b788c0e252dc
frontend-ui-engineering is a skill published in the GitHub repository helderberto/agent-skills (17 stars, last pushed today), licensed MIT. It adds 69 tokens to every session and 674 once invoked, about $0.0003 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 2026-08-30.
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