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 zacharygcook/agent-skills --skill ui-css-performancegit clone --depth 1 https://github.com/zacharygcook/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/zacharygcook/agent-skills/ui-css-performance)<a href="https://agentmods.dev/skills/zacharygcook/agent-skills/ui-css-performance"><img src="https://agentmods.dev/badge/skills/zacharygcook/agent-skills/ui-css-performance/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/zacharygcook/agent-skills/ui-css-performance"><img src="https://agentmods.dev/badge/skills/zacharygcook/agent-skills/ui-css-performance.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 | $0.00051 | $0.00388 |
| Opus 5 | $0.00026 | $0.00194 |
| Sonnet 5 | $0.00010 | $0.00078 |
| Haiku 4.5 | $0.00005 | $0.00039 |
Grade A, and why
ui-css-performance 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.
What it actually says
UI and CSS Performance
Add the smallest UI surface that solves the real task and measure the result when bundle or stylesheet size may change.
Core Rules
- Prefer an existing component or simple local markup before adding a new reusable primitive.
- Add only component-library primitives that product code actually imports.
- Delete dormant components, providers, hooks, forms, and wrappers; source scanners may include them even when the JavaScript bundle does not.
- Declare every directly imported package and remove packages whose final consumer disappears.
- Keep utility-class names as static strings or finite maps of complete strings. Avoid dynamically assembled class fragments that scanners cannot discover reliably.
- Do not broaden content globs, enable plugins, or import global styles without measuring their effect.
- Keep admin/editor CSS out of public routes unless those routes need it.
New Primitive Checklist
- Confirm no existing primitive already fits.
- Add only the primitive and direct dependencies it needs.
- Import it from real application code in the same change.
- Run the repository's UI lint, unused-code/dependency scan, typecheck, and build.
- If it remains unused, remove it instead of suppressing the check.
Measure
Use repository-native build and bundle tooling. Compare the relevant route chunks and emitted CSS before and after when the change adds a library, plugin, global stylesheet, animation system, icon set, or broad content glob. Record units and whether sizes are raw, minified, or compressed.
If exact bundle tooling is unavailable, report that limitation and use bounded evidence such as emitted asset sizes and import reachability. Do not claim a performance win without measurement.
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.
- 8d ago First seen · 33 lines · 51 tokens per session scan A 51636253b230
ui-css-performance is a skill published in the GitHub repository zacharygcook/agent-skills (2 stars, last pushed 1mo ago), licensed MIT. It adds 51 tokens to every session and 388 once invoked, about $0.0003 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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