Generates throwaway, single-file HTML logic demos or multi-variant UI routes to validate state models or visual designs before production implementation.
Not measured yet. Every skill is tested against the bare model on its own example requests; results appear here.
Security scan: clean · 2026-10-24 · 4 files · ran in sandbox no network calls, shell tricks, credential access or instruction tampering found in its files.
Try asking
Say it in your own words; the assistant finds this recipe by itself. Examples:
“Jeg er i tvivl om, om vores tilstandsmaskine håndterer rabatter korrekt. Lav en hurtig HTML-demo, jeg kan klikke mig igennem.”
“Lav en prototype med tre forskellige udgaver af login-skærmen, så vi kan se, hvilken der ser bedst ud.”
“Vi skal tjekke, om den nye onboarding-flow giver mening. Gør en interaktiv demo uden at gemme data i databasen.”
“I'm not sure if the cart state machine handles tax calculation correctly when items are removed. Can you build a quick HTML demo to test this?”
“Make a throwaway page with three different layouts for the settings modal so I can see which one feels less cluttered.”
“We need to check if the user onboarding flow makes sense. Create a clickable prototype that walks through the steps without saving anything to the database.”
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Do not use this for building production-ready features, adding unit tests, or implementing persistent data storage solutions. For these requests, use a standard feature development or backend implementation skill instead. It is also not suitable for refactoring existing stable code or fixing bugs in live systems.
Details
When it is the right choice
Use this when a user needs to visually verify if a complex state transition or business logic behaves as expected without running the full application. It is also appropriate when a designer or developer wants to quickly compare multiple distinct UI layouts or interaction patterns for a specific feature. This skill is ideal for early-stage design questions where the goal is to gain insight, not to build production-ready code.
The full recipe the assistant reads
Prototype
A prototype is throwaway code that answers a question. The question decides the shape.
Pick a branch
Identify which question is being answered, using 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 a single shareable HTML file (free-play buttons plus tabbed guided walkthroughs) 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, so 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 a single HTML file the user double-clicks. Either way, no thinking required to start it.
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.
Capture it when done. Fold any validated decision into the real code, then capture the prototype itself as a primary source: commit it to a throwaway branch, out of main, and leave a context pointer to that branch on the implementation issue. Capture the answer too (the verdict and the question it settled) in the issue or a commit. The main branch keeps only the validated decision.
Files in this skill (5)
LICENSE
LOGIC.md
SKILL.md
UI.md
agents/openai.yaml
Where it comes from
Vendored from mattpocock/skills, commit 5beb35b040e3, path skills/engineering/prototype, licence MIT. The upstream licence file ships inside the skill.