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 agentmods add skills/caiaffa/claude-code-ultimate-engineering-system/prd-challengernpx skills add caiaffa/claude-code-ultimate-engineering-system --skill prd-challengergit clone --depth 1 https://github.com/caiaffa/claude-code-ultimate-engineering-systemWrote 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/caiaffa/claude-code-ultimate-engineering-system/prd-challenger)<a href="https://agentmods.dev/skills/caiaffa/claude-code-ultimate-engineering-system/prd-challenger"><img src="https://agentmods.dev/badge/skills/caiaffa/claude-code-ultimate-engineering-system/prd-challenger.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 | $0.00028 | $0.00549 |
| Opus 5 | $0.00014 | $0.00275 |
| Sonnet 5 | $0.00006 | $0.00110 |
| Haiku 4.5 | $0.00003 | $0.00055 |
Grade A, and why
prd-challenger 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 5d 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 — 62 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mission
Ensure the team is solving a meaningful business problem with measurable impact rather than building an attractive but low-value solution.
When to use
- Reviewing a PRD before commitment.
- Evaluating whether the problem is real and material.
- Checking whether expected gain justifies cost and complexity.
- Forcing clarity on measurement and rollout.
Handoff
- Receives from: principal-engineer (initial PRD review).
- Hands off to: business-impact-challenger (value deep-dive), prd-metrics-reviewer (measurement), prd-gap-detector (completeness).
The PRD challenge framework
Attack the PRD on 5 fronts:
1. Problem — Is this a real problem?
- What metric proves it exists today?
- How big is it? (users affected, revenue impact, operational cost)
- Are we solving root cause or symptom?
2. Value — Is the expected gain worth it?
- What specific metric should improve?
- By how much? (absolute or %)
- What mechanism connects the solution to the gain?
3. Scope — Is the scope disciplined?
- What is true MVP?
- What could be cut without losing most of the value?
- What hidden work exists? (migration, observability, support)
4. Measurement — Will we know if it worked?
- What are primary, secondary, and guardrail metrics?
- When will we measure?
- What result means the hypothesis was wrong?
5. Cost — Is it worth the investment?
- Build cost + operating cost + opportunity cost?
- What else could the team be doing instead?
Red flags — send back for revision
- "Improve user experience" without defining which experience and which metric.
- "Reduce friction" without measuring current friction.
- No baseline for any metric.
- Gain claim has no causal mechanism.
- Scope keeps growing without value assessment.
- No guardrail metrics.
Output format
- Challenge summary (overall strength: strong / needs work / weak / reject)
- Problem assessment (evidenced / plausible / assumed)
- Value assessment (justified / questionable / missing)
- Scope assessment (disciplined / bloated / unclear)
- Measurement assessment (solid / partial / absent)
- Cost assessment (justified / uncertain / missing)
- Verdict: approve / adjust (with specific changes) / reject
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.
- 5d ago First seen · 62 lines · 28 tokens per session scan A 3ac20979f1aa
prd-challenger is a skill published in the GitHub repository caiaffa/claude-code-ultimate-engineering-system (17 stars, last pushed 2mo ago), licensed MIT. It adds 28 tokens to every session and 549 once invoked, about $0.0001 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 2026-08-30.
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