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 Kastalien-Research/thoughtbox --skill frontend-design-principlesgit clone --depth 1 https://github.com/Kastalien-Research/thoughtboxWrote 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/kastalien-research/thoughtbox/frontend-design-principles)<a href="https://agentmods.dev/skills/kastalien-research/thoughtbox/frontend-design-principles"><img src="https://agentmods.dev/badge/skills/kastalien-research/thoughtbox/frontend-design-principles/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/kastalien-research/thoughtbox/frontend-design-principles"><img src="https://agentmods.dev/badge/skills/kastalien-research/thoughtbox/frontend-design-principles.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 | $0.00044 | $0.02497 |
| Opus 5.5 | $0.00018 | $0.00999 |
| Sonnet 5.5 | $0.00009 | $0.00499 |
| Haiku 4.5 | $0.00004 | $0.00250 |
Grade A, and why
frontend-design-principles 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 — 210 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Frontend Design Principles
Build frontend interfaces with craft and intention.
Scope & Routing
After reading this file, load additional guidance based on what you're building:
Load app.md when building:
- Dashboards and admin interfaces
- Settings panels and configuration screens
- Internal tools and SaaS products
- Data-heavy interfaces with tables, forms, lists
- Any interface where users work repeatedly
Load marketing.md when building:
- Landing pages and marketing sites
- Promotional materials and announcements
- Creative artifacts and posters
- Public-facing pages meant to impress
- Any interface where first impression matters most
If unclear, ask. Some projects blend both — a SaaS marketing site needs marketing.md, but its actual product dashboard needs app.md.
Why This Process Exists
You will generate generic output. Your training has seen thousands of dashboards, landing pages, marketing sites. The patterns are strong.
You can follow the entire process below — explore the domain, name a signature, state your intent — and still produce a template. Warm colors on cold structures. Friendly fonts on generic layouts. "Kitchen feel" that looks like every other app.
This happens because intent lives in prose, but code generation pulls from patterns. The gap between them is where defaults win.
The process below helps. But process alone doesn't guarantee craft. You have to catch yourself.
Where Defaults Hide
Defaults don't announce themselves. They disguise themselves as infrastructure — the parts that feel like they just need to work, not be designed.
Typography feels like a container. Pick something readable, move on. But typography isn't holding your design — it IS your design. The weight of a headline, the personality of a label, the texture of a paragraph. These shape how the product feels before anyone reads a word. A bakery management tool and a trading terminal might both need "clean, readable type" — but the type that's warm and handmade is not the type that's cold and precise. If you're reaching for your usual font, you're not designing.
What ships with it
3 files 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.
- 1mo ago First seen · 210 lines · 44 tokens per session scan A e11541d0ad5d
frontend-design-principles is a skill published in the GitHub repository Kastalien-Research/thoughtbox (65 stars, last pushed 3mo ago), licensed MIT. It adds 44 tokens to every session and 2,497 once invoked, about $0.0002 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 2026-09-03.
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