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 levnikolaevich/claude-code-skills --skill ln-73-system-design-proposal-buildergit clone --depth 1 https://github.com/levnikolaevich/claude-code-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/levnikolaevich/claude-code-skills/ln-73-system-design-proposal-builder)<a href="https://agentmods.dev/skills/levnikolaevich/claude-code-skills/ln-73-system-design-proposal-builder"><img src="https://agentmods.dev/badge/skills/levnikolaevich/claude-code-skills/ln-73-system-design-proposal-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/levnikolaevich/claude-code-skills/ln-73-system-design-proposal-builder"><img src="https://agentmods.dev/badge/skills/levnikolaevich/claude-code-skills/ln-73-system-design-proposal-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 | $0.00032 | $0.01687 |
| Opus 5 | $0.00016 | $0.00843 |
| Sonnet 5 | $0.00006 | $0.00337 |
| Haiku 4.5 | $0.00003 | $0.00169 |
Grade A, and why
ln-73-system-design-proposal-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 4d 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 — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.
System Design Proposal Builder
Goal: Create a proportionate, evidence-backed target system design that turns requirements into explicit boundaries, contracts, data flow, failure behavior, operations, and tradeoffs. Change only the approved design document; do not implement, audit, or approve the delivery.
Execution contract: The ordered checkboxes are the Definition of Done. Track every item internally as PENDING, PROVEN with concrete evidence, CLEARED with evidence that its condition is absent, or UNPROVEN with a gap; reading, delegation, or tool failure is not proof. Reconcile items after each section. Before returning, resolve all PENDING and count only PROVEN and CLEARED; apply the skill's verdict and approval rules to every gap.
Preserve user intent, scope, and existing authorization. Continue authorized work; ask only for consequential unresolved choices or required external approval. Scale depth to material risk without silently skipping checks. Preserve dependency and safety ordering; otherwise choose the verification method appropriate to each obligation.
Tool Routing
| Need | Preferred capability | Fallback |
|---|---|---|
| Requirements and constraints | Approved requirements, baseline, decisions, and direct stakeholder input | Mark material gaps and ask the smallest decision question |
| Current implementation and conventions | Repository search, manifests, entrypoints, and architecture artifacts | Treat as greenfield only when the user or repository establishes that fact; otherwise mark current state UNKNOWN and return REVISE or BLOCKED when the gap can change boundaries, compatibility, or migration |
| External capabilities and limits | Current official documentation and specifications | Mark claims UNVERIFIED; avoid vendor-dependent commitment |
| Estimates | Reproducible arithmetic from sourced workload assumptions | Use ranges and sensitivity; never present estimates as measurements |
| Document mutation | Minimal patch to the approved target-design artifact | Return BLOCKED if scope or path is unsafe |
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.
- 4d ago Changed · -8 lines · -9 tokens per session 42fdd552fe53
- 10d ago First seen · 106 lines · 41 tokens per session scan A c11a183cd704
ln-73-system-design-proposal-builder is a skill published in the GitHub repository levnikolaevich/claude-code-skills (559 stars, last pushed 5d ago), licensed MIT. It adds 32 tokens to every session and 1,687 once invoked, about $0.0002 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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