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 MichelKerkmeester/skilled-agent-harness_spec-driven-loops --skill sk-design-fundamentalsgit clone --depth 1 https://github.com/MichelKerkmeester/skilled-agent-harness_spec-driven-loopsWrote 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/michelkerkmeester/skilled-agent-harness_spec-driven-loops/sk-design-fundamentals)<a href="https://agentmods.dev/skills/michelkerkmeester/skilled-agent-harness_spec-driven-loops/sk-design-fundamentals"><img src="https://agentmods.dev/badge/skills/michelkerkmeester/skilled-agent-harness_spec-driven-loops/sk-design-fundamentals/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/michelkerkmeester/skilled-agent-harness_spec-driven-loops/sk-design-fundamentals"><img src="https://agentmods.dev/badge/skills/michelkerkmeester/skilled-agent-harness_spec-driven-loops/sk-design-fundamentals.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 | $0.00052 | $0.08432 |
| Opus 5 | $0.00026 | $0.04216 |
| Sonnet 5 | $0.00010 | $0.01686 |
| Haiku 4.5 | $0.00005 | $0.00843 |
Grade A, and why
sk-design-fundamentals 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 4d 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.
This is a copy
89% identical to sk-design — 611 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 526 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Visual Design
Visual design is not talent. It is a small set of systems decisions made once, plus a handful of techniques for building hierarchy, a set of interaction details that make a screen behave correctly, and a motion model that keeps it feeling human.
Most of that is not about screens. A spacing scale, a type scale, a colour ramp and a hierarchy pyramid decide a slide, a printed page and a report layout as much as they decide a component. The sections below say which parts carry to every surface and which are genuinely screen-only, so a deck question gets the systems and skips the focus rings.
The single biggest cause of amateur-looking UI is picking values ad hoc — 17px here, #3B82F6 there, lighten(5%) for a hover state, 400ms because it seemed smooth. Design from a scale, always.
Boundary. This skill decides values and behavior when UI is being built, fixed, or reviewed. It is prescriptive and emits CSS. It does not measure an existing site —
sk-design-md-generatorextracts a live surface's real CSS into a measured Style Reference, and when such a reference exists its measured values win over the defaults here. See Section 7.
What ships with it
28 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.
- assets/token-starter-set.md 6.0 KB
- assets/tokens.css 7.9 KB
- benchmark/README.md 926 B
- benchmark/reports/README.md 1.2 KB
- changelog/v1.0.0.0.md 6.8 KB
- manual-testing-playbook/boundary/extraction-defers-to-md-generator.md 5.3 KB
- manual-testing-playbook/boundary/implementation-defers-to-sk-code.md 4.8 KB
- manual-testing-playbook/conflict-handling/contrast-escape-hatches.md 5.1 KB
- manual-testing-playbook/conflict-handling/project-system-precedence.md 5.0 KB
- manual-testing-playbook/conflict-handling/shadow-system-consistency.md 5.1 KB
- manual-testing-playbook/manual-testing-playbook.md 9.3 KB
- manual-testing-playbook/routing/diagnose-entry.md 5.8 KB
- manual-testing-playbook/routing/motion-entry.md 5.2 KB
- manual-testing-playbook/routing/procedure-entry.md 5.2 KB
- manual-testing-playbook/routing/review-entry.md 5.5 KB
- manual-testing-playbook/value-discipline/no-runtime-shades.md 5.0 KB
- manual-testing-playbook/value-discipline/on-scale-values.md 5.0 KB
- manual-testing-playbook/value-discipline/unit-discipline.md 5.1 KB
- README.md 11 KB
- references/build-procedure.md 4.8 KB
- references/color-system.md 8.8 KB
- references/depth-and-detail.md 19 KB
- references/diagnosis-table.md 8.9 KB
- references/hierarchy.md 6.4 KB
- references/interaction-craft.md 8.5 KB
- references/motion-principles.md 10 KB
- references/review-checklist.md 7.1 KB
- references/ux-laws.md 7.6 KB
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.
- 4d ago Changed · +4 tokens per session 042113f2a9e9
- 5d ago First seen · 526 lines · 48 tokens per session scan A adb86695a463
sk-design-fundamentals is a skill published in the GitHub repository MichelKerkmeester/skilled-agent-harness_spec-driven-loops (35 stars, last pushed today), licensed MIT. It adds 52 tokens to every session and 8,432 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 89% identical to sk-design, differing in 611 lines, and is treated as a copy.
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