SkillVerdict
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prototype

Install mattpocock/skills

Builds a one-file HTML logic demo or switchable UI variants to answer one design question. No scripts, MIT, but it commits and comments on issues.

Verified · Repo on GitHub

What it does

Builds throwaway code to answer one design question, in one of two shapes. For "does this logic or state model feel right?" it writes a single self-contained HTML file: the logic as a small pure module, the full state shown after every click, free-play buttons and tabbed walkthroughs a non-developer can drive. For "what should this look like?" it puts three to five structurally different UI variants on one route, switched by a ?variant= URL parameter and a floating bottom bar that is hidden in production builds.

Who made it / license / last checked

Matt Pocock (mattpocock/skills) · License: MIT (repo LICENSE) · Repo last commit checked: 2026-10-31 (the skill folder last changed on 2026-08-19)

Install

claude plugin install mattpocock-skills@claude-plugins-official

From the repo README (Claude Code route; it installs the whole pack). For other agents the README gives npx skills@latest add mattpocock/skills -a <agent>. We did not run the installer.

What files / scripts it runs

SKILL.md (2,931 bytes), LOGIC.md (6,036 bytes) and UI.md (6,913 bytes) as instructions, plus an agents/openai.yaml display file. No scripts. The model can invoke it on its own (no disable-model-invocation). It acts through your agent's tools: it writes prototype files next to the code they are for, adds a run command to your task runner and, when done, commits the prototype to a throwaway branch and leaves a pointer on the implementation issue.

Pros

  • Picks the artifact from the question, and says which assumption it made when the question is unclear
  • Keeps the logic pure and liftable, so the part worth keeping moves into the real module
  • No persistence by default; anything that must touch a database uses a scratch one named to be wiped
  • Plain, short instructions with clear anti-patterns (no tests, no framework, no generalising)

Cons

  • It writes code into your repo and asks the agent to commit a branch and comment on an issue: check what it touches before you approve
  • Prototypes skip tests and error handling on purpose; the skill relies on naming and a production gate to keep them out of main
  • Can trigger on its own whenever you mention a prototype or a UI idea

Alternatives

emilkowalski/skills also publishes a skill named prototype (a different skill, not reviewed here); a plain design-tool mockup when the question is only visual.

Notes

Skills.sh listed prototype at 1.0M installs on 4 Nov 2026. The repo also explains the idea at more length in docs/engineering/prototype.md.

Sources

Verified on 2026-11-04 from a fresh clone of the repo (commit 4ae2317, 2026-10-31; folder commit 3216582, 2026-08-19; sizes are git blob bytes) and the skills.sh leaderboard fetched that day. Nothing was installed or executed. Install counts are distribution, not quality.