Build a throwaway prototype to answer a design question.
SkillScore63Maintained
Automatic
◆Coding pack
Last verified 9/26/2026
What it changes
Passed 14 of 22 test cases with the skill, and 7 of 22 without it.
Without skill33%
With skill63%
Checks it passed that the model alone missed
The response explicitly advises omitting unit tests.
The UI prototype renders a floating bottom bar to switch variations.
The prototype is placed in the queue library directory next to worker.ts.
and 8 more in the full report
9 fixed6 passed either way7 still failing2 broke
Pass-rate lift
+29 pp
Tokens
+22%
Agent turns
0%
Response time
-2%
Model gemini-3.6-flashMeasured 9/26/2026v115 of 24 cases passed with skill · 22 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 9 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 9
Prompt
I'm prototyping a complex permissions engine state model. Can I supply this as a Node.js CLI script that prints JSON to the terminal?
What was checked, without and with the skill
Checked
Without skill
With skill
The response specifies that the logic prototype must be a single standalone HTML file.
Missed
Passed
case-23 · gemini-3.6-flash · 9/26/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md21 linessingle file
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.