Borrowing it
Nothing to install: this file belongs to BilLogic/design-harnessing-kit. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/BilLogic/design-harnessing-kit/main/.agent/skills/prototyper/SKILL.mdgit clone --depth 1 https://github.com/BilLogic/design-harnessing-kitWrote 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/billogic/design-harnessing-kit/prototyper)<a href="https://agentmods.dev/skills/billogic/design-harnessing-kit/prototyper"><img src="https://agentmods.dev/badge/skills/billogic/design-harnessing-kit/prototyper/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/billogic/design-harnessing-kit/prototyper"><img src="https://agentmods.dev/badge/skills/billogic/design-harnessing-kit/prototyper.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 | $0.00031 | $0.00522 |
| Opus 5 | $0.00015 | $0.00261 |
| Sonnet 5 | $0.00006 | $0.00104 |
| Haiku 4.5 | $0.00003 | $0.00052 |
Grade A, and why
prototyper 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 9d 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 — 54 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Prototyper Skill
When to Activate
- User asks to design, prototype, create, or build UI
- User asks to generate code for a design
Workflow
Follow this sequence — do not skip steps.
Step 1: Check for a Plan
Before prototyping, check if a design plan exists (requirements, layout strategy, component choices).
- No plan yet? → Hand off to the Consultant skill first. The Consultant will research, analyze, and produce a plan. Come back here when the plan is ready.
- Plan exists? → Proceed to Step 2.
Step 2: Check for an Existing Prototype
- Starting from scratch? → Use Stitch MCP to generate an initial design from the plan. Present the Stitch output to the user for review. Once approved, proceed to code implementation.
- Existing prototype? → Review it against the plan and proceed to refinement.
Step 3: Implement in Code
- Read
context/design-system/components/index.md�� never invent components - Read
references/output-format.md— follow code conventions and token mapping - Load other references on demand as needed (progressive disclosure)
- Read
knowledge/lessons-learned.md— avoid known mistakes
Step 4: Present and Review
- Present the implementation on localhost (
npm run app:dev) - Walk the user through the design decisions
- Suggest using the Critic skill to evaluate the result
Step 5: Figma Sync (Optional)
If the user wants to refine the design visually:
- Use Figma MCP to replicate the design into a Figma file
- User fine-tunes layout, spacing, and visual details in Figma
- Read the updated Figma file back via Figma MCP and apply changes to code
References (load on demand — not all at once)
references/output-format.md— code conventions, imports, token mapping, canonical sourcesreferences/component-index.md— compact component listreferences/styles-summary.md— all style token valuesreferences/foundations-summary.md— layout, spacing, accessibilityreferences/interaction-patterns.md— common UI patterns for landing pages
What ships with it
5 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.
- 9d ago First seen · 54 lines · 31 tokens per session scan A 4dfc80177c06
prototyper is a skill published in the GitHub repository BilLogic/design-harnessing-kit (2 stars, last pushed 5mo ago), licensed MIT. It adds 31 tokens to every session and 522 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 2026-08-31.
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