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 axiomantic/spellbook --skill reviewing-design-docsgit clone --depth 1 https://github.com/axiomantic/spellbookWrote 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/axiomantic/spellbook/reviewing-design-docs)<a href="https://agentmods.dev/skills/axiomantic/spellbook/reviewing-design-docs"><img src="https://agentmods.dev/badge/skills/axiomantic/spellbook/reviewing-design-docs/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/axiomantic/spellbook/reviewing-design-docs"><img src="https://agentmods.dev/badge/skills/axiomantic/spellbook/reviewing-design-docs.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 | $0.00092 | $0.01131 |
| Opus 5.5 | $0.00037 | $0.00452 |
| Sonnet 5.5 | $0.00018 | $0.00226 |
| Haiku 4.5 | $0.00009 | $0.00113 |
Grade A, and why
reviewing-design-docs 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 1mo 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 — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Invariant Principles
- Specification sufficiency determines implementation success. Underspecified designs force implementers to guess, causing divergent implementations and rework.
- Method names are suggestions, not contracts. Inferred behavior from naming is fabrication until verified against source.
- Vague language masks missing decisions. "Standard approach", "as needed", "TBD" defer design work to implementation phase where it costs 10x more.
- Complete != comprehensive. Document completeness means every item either specified or explicitly N/A with justification.
Inputs
| Input | Required | Description |
|---|---|---|
| Design document | Yes | Markdown/text file containing technical specification, architecture doc, or design proposal |
| Source codebase | No | Existing code to verify interface claims against |
| Implementation context | No | Target platform, constraints, prior decisions |
Outputs
| Output | Type | Description |
|---|---|---|
| Findings report | Inline | Scored inventory with SPECIFIED/VAGUE/MISSING verdicts per category |
| Remediation plan | Inline | Prioritized P1/P2/P3 fixes with acceptance criteria |
| Factcheck escalations | Inline | Claims requiring verification before implementation |
Reasoning Schema
<analysis>
[Document section under review]
[Specific claim or specification]
[What implementation decision this enables or blocks]
</analysis>
<reflection>
[Could I code against this RIGHT NOW?]
[What would I have to invent/guess?]
[Verdict: SPECIFIED | VAGUE | MISSING]
</reflection>
Example verdict: "Authentication timeout: 30s" → SPECIFIED. "Retry on failure: standard approach" → VAGUE (retry count, backoff unspecified). "Rate limiting" → MISSING (no mention).
Phase 1: Document Inventory
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.
- 1mo ago First seen · 130 lines · 92 tokens per session scan A 2daba6d6db37
reviewing-design-docs is a skill published in the GitHub repository axiomantic/spellbook (10 stars, last pushed 2d ago), licensed MIT. It adds 92 tokens to every session and 1,131 once invoked, about $0.0004 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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