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 helderberto/agent-skills --skill prototypegit clone --depth 1 https://github.com/helderberto/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/helderberto/agent-skills/prototype)<a href="https://agentmods.dev/skills/helderberto/agent-skills/prototype"><img src="https://agentmods.dev/badge/skills/helderberto/agent-skills/prototype/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/helderberto/agent-skills/prototype"><img src="https://agentmods.dev/badge/skills/helderberto/agent-skills/prototype.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 | $0.00066 | $0.00722 |
| Opus 5.5 | $0.00026 | $0.00289 |
| Sonnet 5.5 | $0.00013 | $0.00144 |
| Haiku 4.5 | $0.00007 | $0.00072 |
Grade A, and why
prototype 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 19d 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
84% identical to prototype — 16 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 — 32 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Prototype
A prototype is throwaway code that answers a question. The question decides the shape.
Pick a branch
Identify which question is being answered — from the user's prompt, the surrounding code, or by asking if the user is around:
- "Does this logic / state model feel right?" → logic.md. Build one self-contained HTML file — free-play buttons plus guided scenario tabs, in domain language — that pushes the state machine through cases that are hard to reason about on paper, and that a non-developer can drive.
- "What should this look like?" → ui.md. Generate several radically different UI variations on a single route, switchable via a URL search param and a floating bottom bar.
The two branches produce very different artifacts — getting this wrong wastes the whole prototype. If the question is genuinely ambiguous and the user isn't reachable, default to whichever branch better matches the surrounding code (a backend module → logic; a page or component → UI) and state the assumption at the top of the prototype.
Rules that apply to both
- Throwaway from day one, and clearly marked as such. Locate the prototype code close to where it will actually be used (next to the module or page it's prototyping for) so context is obvious — but name it so a casual reader can see it's a prototype, not production. For throwaway UI routes, obey whatever routing convention the project already uses; don't invent a new top-level structure.
- Trivial to run. A UI prototype starts from one command in the project's task runner —
pnpm <name>,python <path>,bun <path>, etc. A logic demo is one HTML file the user double-clicks. - No persistence by default. State lives in memory. Persistence is the thing the prototype is checking, not something it should depend on. If the question explicitly involves a database, hit a scratch DB or a local file with a clear "PROTOTYPE — wipe me" name.
- Skip the polish. No tests, no error handling beyond what makes the prototype runnable, no abstractions. The point is to learn something fast.
- Surface the state. After every action (logic) or on every variant switch (UI), print or render the full relevant state so the user can see what changed.
- Keep it off main when done. Fold the validated decision into the real code, then commit the prototype itself to a
prototype/<name>branch as a primary source, pointed at from the issue or spec that uses it. Main keeps only the decision.
What ships with it
2 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.
- 19d ago Changed · +2 tokens per session 20a520463847
- 1mo ago Changed · -12 tokens per session f8a0aa40d091
- 1mo ago Changed · -4 tokens per session cb25b65b267e
- 1mo ago First seen · 32 lines · 80 tokens per session scan A a120bbefec65
prototype is a skill published in the GitHub repository helderberto/agent-skills (19 stars, last pushed yesterday), licensed MIT. It adds 66 tokens to every session and 722 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 84% identical to prototype, differing in 16 lines, and is treated as a copy.
Other skills, from other repositories
frontend-ui-engineering
Builds production-quality, accessible, responsive user-facing UIs. Use when building or modifying interfaces and pages, creating components, implementing layouts, meeting WCAG accessibility requirements, managing state, or when the output needs to look and feel production-quality rather than AI-generated.
shadcnui
Expert shadcn/ui assistance covering Radix UI primitives, Tailwind CSS styling, copy-paste architecture, and accessibility. Use when building modern React component systems and accessible design systems.
bootstrap
Expert Bootstrap 5 assistance covering 12-column grid system, flexbox utilities, components, and responsive breakpoints. Use when rapidly prototyping responsive, mobile-first web layouts.
chakraui
Expert Chakra UI assistance covering accessible React components, theme tokens, style props, and dark mode. Use when building modular, accessible React component libraries and dashboards.
materialui
Expert Material UI (MUI) assistance covering Emotion styled components, theme customization, DataGrid, and accessible icons. Use when building React enterprise dashboards with Google's Material Design.
vuetify
Expert Vuetify assistance covering Material Design components, data tables, responsive layouts, and themes for Vue 3. Use when rapidly building enterprise dashboards and back-office tools in Vue.