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 richfrem/agent-plugins-skills --skill prototype-buildergit clone --depth 1 https://github.com/richfrem/agent-plugins-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/richfrem/agent-plugins-skills/prototype-builder)<a href="https://agentmods.dev/skills/richfrem/agent-plugins-skills/prototype-builder"><img src="https://agentmods.dev/badge/skills/richfrem/agent-plugins-skills/prototype-builder/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/richfrem/agent-plugins-skills/prototype-builder"><img src="https://agentmods.dev/badge/skills/richfrem/agent-plugins-skills/prototype-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00029 | $0.00438 |
| Opus 5.5 | $0.00012 | $0.00175 |
| Sonnet 5.5 | $0.00006 | $0.00088 |
| Haiku 4.5 | $0.00003 | $0.00044 |
Grade A, and why
prototype-builder 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 17d 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.
What it actually says
Prototype Builder (prototype-builder)
Orchestrates the prototype build cycle from approved Discovery Plans to working prototypes and SME walkthroughs.
Contents
Critical Constraints
- Hard gate: No building may commence without an approved Discovery Plan in
exploration/discovery-plans/. - Coordinate build cycles without implementing code directly; delegate components to
subagent-driven-prototyping. - Always record raw walkthrough feedback to
exploration/captures/walkthrough-notes.md.
Quick start
- Verify approved Discovery Plan exists in
exploration/discovery-plans/. - Confirm layout direction with
visual-companioninexploration/captures/layout-direction.md. - Dispatch component construction to
subagent-driven-prototypingand guide SME walkthrough.
Workflow
- Gate Check: Verify plan approval in
exploration/discovery-plans/; halt and redirect to planning if unapproved. - Layout Direction: Invoke
visual-companionto capture wireframes or layout directions. - Component Build: Invoke
subagent-driven-prototypingto assemble parts inexploration/prototype/. - SME Walkthrough: Walk the SME through main user journeys and document observations in
exploration/captures/walkthrough-notes.md. - Phase Handoff: Synthesize notes into
exploration/captures/prototype-notes.mdand report completion.
Verification
- Confirm
exploration/prototype/contains runnable prototype assets. - Validate that walkthrough notes capture all SME feedback and blocker items.
- Ensure all acceptance criteria from the Discovery Plan are evaluated.
References
What ships with it
4 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.
- 17d ago Changed · -77 lines · -47 tokens per session 9193f10c959a
- 1mo ago First seen · 118 lines · 76 tokens per session scan A 783984366026
prototype-builder is a skill published in the GitHub repository richfrem/agent-plugins-skills (7 stars, last pushed yesterday), licensed MIT. It adds 29 tokens to every session and 438 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-03.
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