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 ljucask/pureinn-product-development --skill pm-prototypegit clone --depth 1 https://github.com/ljucask/pureinn-product-developmentWrote 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/ljucask/pureinn-product-development/pm-prototype)<a href="https://agentmods.dev/skills/ljucask/pureinn-product-development/pm-prototype"><img src="https://agentmods.dev/badge/skills/ljucask/pureinn-product-development/pm-prototype.svg" alt="Measured on agentmods" 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 | $0.00154 | $0.05935 |
| Opus 5 | $0.00077 | $0.02967 |
| Sonnet 5 | $0.00031 | $0.01187 |
| Haiku 4.5 | $0.00015 | $0.00594 |
Grade A, and why
pm-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 7d 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 — 426 lines — stays where its author put it; the contents beside it link to each section on GitHub.
PM - Prototype (validate before real build)
Agent mode (--agent)
Supports --agent: runs autonomously in a subagent, drafts the artifact from existing inputs, and returns a short summary + coverage note.
- No flag → interactive (default); if inputs are heavy, offer agent mode.
--agent→ obey. First check inputs are complete. Anything missing: do NOT invent it - mark[ASSUMED - what/why]in the output and summary. Never hallucinate to fill a gap.
What this skill does
Produces a tool-ready prototype spec for a scoped chunk of the product, so you can validate a flow, a UX hypothesis, a concept, or technical feasibility with a prototyping tool before anyone writes production code.
The scope is whatever you point at, with no limit:
- a single feature (linked to a Feature Card),
- a PRD initiative (a larger new part),
- the whole product,
- or any slice ("for this user type, test this part of the functionality").
Cross-phase. Like adding a hypothesis or running a validation, this skill has no fixed home in the sequence. Run it whenever there is genuine uncertainty worth de-risking cheaply - during discovery (concept desirability), before a PRD initiative (flow/scope), or inside Phase 6 before a feature enters build (UX/interaction).
Two modes (same skill, same file):
| Mode | When | What it does |
|---|---|---|
| Spec mode (default) | You want to build a prototype | Gate-check → ingest inputs → compile tool-ready spec → hand off to tool |
| Result mode (re-run) | The prototype exists, you have a result | Capture what the prototype proved/disproved → decision → cascade to Feature Card / hypotheses |
What the skill is NOT: it does not replace pm-feature-design (JIT production spec) and it does not build the prototype's production version. A prototype is a throwaway or a reference, not the build.
Hard rule: the skill does not guess
The prototype spec is only as good as its inputs, and a guessed input produces a wrong prototype that validates the wrong thing. So:
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.
- 7d ago First seen · 426 lines · 154 tokens per session scan A 0f86e49ffa9c
pm-prototype is a skill published in the GitHub repository ljucask/pureinn-product-development (2 stars, last pushed 28d ago), licensed MIT. It adds 154 tokens to every session and 5,935 once invoked, about $0.0008 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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