spellbook: Skill for Claude Code

.claude/skills/spellbook-auditing/SKILL.md

spellbook-auditing is a skill for Claude Code from axiomantic/spellbook. It costs 42 tokens per session (4,102 once invoked), scanned A, original, MIT.

A meta-review process for the spellbook project, meaning the collection of its skills, commands, documentation, and prompts. It uses parallel reviewers to fact-check content, improve instructions, reduce unnecessary text, and find possible tool integrations.

In plain words
What is it for?
It is for auditing the spellbook itself and producing evidence-based, actionable improvements for its documentation and agent instructions.
Why use it?
It helps reveal inaccurate guidance, inefficient instructions, wasted context, and missing opportunities to automate parts of the project.

Skill for Claude Code

Written for Claude Code: installed under .claude/. Also seen: mentions subagents; names the AskUserQuestion tool.

This is axiomantic/spellbook's own configuration. It tells Claude Code how to work on spellbook itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything spellbook configures →

Reuse

Borrowing it

Nothing to install: this file belongs to axiomantic/spellbook. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/axiomantic/spellbook/main/.claude/skills/spellbook-auditing/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/axiomantic/spellbook

Made for: Claude Code.

Wrote 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.

agentmods badge for spellbook-auditing

README.md
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Your own site
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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.

agentmods 80×15 button for spellbook-auditing

Your own site · 80×15
<a href="https://agentmods.dev/skills/axiomantic/spellbook/spellbook-auditing"><img src="https://agentmods.dev/badge/skills/axiomantic/spellbook/spellbook-auditing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 42 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,102 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00042 $0.04102
Opus 5 $0.00021 $0.02051
Sonnet 5 $0.00008 $0.00820
Haiku 4.5 $0.00004 $0.00410

Measured 9d ago against content hash bb5c21feabf7, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

spellbook-auditing 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 9d 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.

.claude/skills/spellbook-auditing/SKILL.md · 567 lines

How it starts

The opening of the file, as written. The whole thing — 567 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Audit Spellbook

You are auditing the spellbook project itself. This skill orchestrates parallel subagents to comprehensively analyze skills, commands, docs, and prompts for optimization opportunities.

Invariant Principles

  1. Parallelism maximizes audit coverage - All audit agents launch simultaneously; sequential execution wastes context
  2. Token efficiency compounds - Small savings multiply across always-loaded descriptions, skill bodies, and runtime
  3. CSO prevents workflow leak - Descriptions trigger only; workflow in description = Claude follows description not skill
  4. Evidence over claims - Every finding requires file/line/example proof; no unsubstantiated optimization recommendations
  5. Actionable over diagnostic - Report must produce implementable items with clear priority

Trigger Conditions

Use this skill when:

  • User asks to "audit spellbook", "optimize skills", "review spellbook"
  • Before major releases to ensure quality
  • When concerned about token usage or instruction bloat
  • Periodically for maintenance

Execution Flow

Phase 1: Launch Parallel Audit Subagents

Launch ALL of these subagents in a SINGLE message (parallel execution):

1. Factcheck Agent
Audit all documentation in spellbook for factual accuracy.

Files to check:
- README.md
- docs/**/*.md
- CHANGELOG.md
- Any claims in skill/command descriptions

For each claim found:
1. Identify the assertion
2. Verify against: code, external sources, logical consistency
3. Flag unverifiable or incorrect claims

Output: JSON array of {file, line, claim, status: "verified"|"unverified"|"incorrect", evidence}
2. Instruction Engineering Compliance Agent
Audit all instruction files against instruction-engineering principles.

Files: skills/*/SKILL.md, commands/*.md, rules/*.md

Check for:
- Clear role definition
- Explicit trigger conditions
- Structured output formats
- Edge case handling
- Appropriate use of examples (not excessive)
- Action-oriented language
- Avoidance of ambiguity

Output: JSON array of {file, issues: [{principle, violation, suggestion}], score: 0-100}

Read the full file on GitHub · 567 lines

Changes

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.

  1. 9d ago First seen · 567 lines · 42 tokens per session scan A bb5c21feabf7

Subscribe to this mod's changes

spellbook-auditing is a skill published in the GitHub repository axiomantic/spellbook (10 stars, last pushed yesterday), licensed MIT. It adds 42 tokens to every session and 4,102 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 2026-08-31.

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