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/design-doc-writernpx skills add caiaffa/claude-code-ultimate-engineering-system --skill design-doc-writergit 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/design-doc-writer)<a href="https://agentmods.dev/skills/caiaffa/claude-code-ultimate-engineering-system/design-doc-writer"><img src="https://agentmods.dev/badge/skills/caiaffa/claude-code-ultimate-engineering-system/design-doc-writer.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 | $0.00023 | $0.00494 |
| Opus 5 | $0.00012 | $0.00247 |
| Sonnet 5 | $0.00005 | $0.00099 |
| Haiku 4.5 | $0.00002 | $0.00049 |
Grade A, and why
design-doc-writer 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 6d 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 — 53 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mission
Turn ambiguous technical intent into a clear document that supports decision-making, delivery, and risk awareness.
When to use
- Proposing a new system or feature.
- Documenting a migration or redesign.
- Aligning stakeholders on a technical plan.
- Creating an implementation-ready design.
Handoff
- Receives from: principal-engineer (design decision) or backend-platform-engineer (implementation planning).
- Hands off to: adr-reviewer (for formal review), architecture-challenger (for stress test), backend-platform-engineer (for implementation).
Before answering
Identify: audience (builders? reviewers? leadership?), business urgency, scope boundaries, operational constraints, rollout risk, unresolved open questions.
Document structure
1. Context → What situation makes this necessary?
2. Problem → What specifically are we solving? (not the solution!)
3. Goals → What does success look like?
4. Non-goals → What are we explicitly NOT doing?
5. Requirements → Hard constraints (compliance, compatibility, performance)
6. Proposed solution → The design with enough detail to implement
7. Alternatives → What else was considered and why rejected?
8. Risks → What can go wrong? (technical, operational, delivery)
9. Rollout plan → How will this be safely introduced?
10. Success metrics → How will we know this worked?
11. Open questions → What remains unresolved?
Quality checks
- Can a new engineer implement this without asking the author questions?
- Can a reviewer identify the key trade-offs in 5 minutes?
- Does the rollout plan have concrete steps, not just "we'll deploy"?
- Are the success metrics measurable with current tooling?
- Is every "TODO" or "TBD" acknowledged as an open question?
Red flags
- Solution described before problem is clearly stated.
- Goals section lists activities ("build X") instead of outcomes ("reduce Y").
- Alternatives section has only one real option.
- Risks section says "low risk" without analysis.
- No rollout section, or rollout is one sentence.
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.
- 6d ago First seen · 53 lines · 23 tokens per session scan A a08af2d14c39
design-doc-writer is a skill published in the GitHub repository caiaffa/claude-code-ultimate-engineering-system (17 stars, last pushed 2mo ago), licensed MIT. It adds 23 tokens to every session and 494 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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