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 cosmicstack-labs/mercury-agent-skills --skill ui-design-systemgit clone --depth 1 https://github.com/cosmicstack-labs/mercury-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/cosmicstack-labs/mercury-agent-skills/ui-design-system)<a href="https://agentmods.dev/skills/cosmicstack-labs/mercury-agent-skills/ui-design-system"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/ui-design-system/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/cosmicstack-labs/mercury-agent-skills/ui-design-system"><img src="https://agentmods.dev/badge/skills/cosmicstack-labs/mercury-agent-skills/ui-design-system.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00031 | $0.03806 |
| Opus 5 | $0.00015 | $0.01903 |
| Sonnet 5 | $0.00006 | $0.00761 |
| Haiku 4.5 | $0.00003 | $0.00381 |
Grade A, and why
ui-design-system 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 10d 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 — 426 lines — stays where its author put it; the contents beside it link to each section on GitHub.
UI Design System Skill
Core Principles
1. Consistency Over Creativity
A design system's primary value is consistency. Every component, token, and pattern must behave predictably across the entire product surface. Creativity belongs at the product level — the design system provides the reliable foundation.
2. Composability First
Components should be built to compose, not to cover every permutation. A well-designed system lets teams assemble complex interfaces from simple, well-defined building blocks. Prefer composition over configuration.
3. Accessibility Is Not Optional
Accessibility must be baked into every component from day one, not bolted on later. Every component in the system should meet at minimum WCAG 2.1 Level AA. Design tokens for color must account for contrast ratios from the start.
4. Dogfood Your Own System
The design system team should be its own first consumer. If the system doesn't work for its creators, it won't work for the wider organization. Build real features with your components before releasing them.
5. Documentation Is a Feature
Documentation is not an afterthought — it is a first-class deliverable. If a component isn't documented, it doesn't exist. Usage guidelines, code examples, accessibility notes, and design rationale are all required.
Design System Maturity Model
Level 1: Ad Hoc
No centralized system. Components are built per-feature. Inconsistent patterns, duplicated code, and design drift across teams. This is the starting point before formalizing a system.
Level 2: Catalog
A shared component library exists, typically in a single repository. Teams can browse and install components. Basic design tokens may exist. Documentation is sparse or auto-generated. Adoption is voluntary and inconsistent.
Level 3: Standardized
Design tokens are formally defined and used across all products. Components are reviewed for consistency. Documentation is maintained in Storybook. A basic contribution process exists. Most teams participate.
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.
- 10d ago First seen · 426 lines · 31 tokens per session scan A 46f29c98b702
ui-design-system is a skill published in the GitHub repository cosmicstack-labs/mercury-agent-skills (470 stars, last pushed 15d ago), licensed MIT. It adds 31 tokens to every session and 3,806 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 2026-08-30.
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