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 commands/axiomantic/spellbook/write-skill-testgit 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/commands/axiomantic/spellbook/write-skill-test)<a href="https://agentmods.dev/commands/axiomantic/spellbook/write-skill-test"><img src="https://agentmods.dev/badge/commands/axiomantic/spellbook/write-skill-test.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 | $0.00029 | $0.01607 |
| Opus 5 | $0.00015 | $0.00804 |
| Sonnet 5 | $0.00006 | $0.00321 |
| Haiku 4.5 | $0.00003 | $0.00161 |
Grade A, and why
write-skill-test 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 3d 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 — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.
RED-GREEN-REFACTOR Skill Testing
Invariant Principles
- No skill without a failing test first - Writing a skill before observing baseline agent behavior is a violation; delete and start over
- Pressure scenarios must combine multiple pressures - Single-pressure tests do not reveal rationalization patterns; combine time pressure, ambiguity, and temptation
- Verbatim evidence, not summaries - Document exact agent quotes and choices during baseline testing; paraphrasing obscures the failure modes the skill must address
Iron Law
NO SKILL WITHOUT FAILING TEST FIRST
Applies to NEW skills AND EDITS. Write skill before testing? Delete it. Start over. Edit skill without testing? Same violation.
The Iron Law is NOT a ceremony component
There is no waiver, and deliberately no exemption for "pure reference churn" or "docs-only" skill edits. Such an exemption would be self-assessed by the agent making the edit, and "this edit changes no behavior" is precisely the claim a baseline test exists to check — a skill edit that looks inert is the case most likely to be wrong, because skills ARE their text. A test-first rule that can be switched off is not a rule; it is a default.
If the Iron Law is genuinely too heavy for a given change, the correct response is to
make a SMALLER change, not to run a lighter ceremony. Record the Iron Law in
develop_gate_ledger.ceremony.core, never in selected and never in declined.
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.
- 3d ago First seen · 161 lines · 29 tokens per session scan A 7b6de1994216
write-skill-test is a command published in the GitHub repository axiomantic/spellbook (10 stars, last pushed 2d ago), licensed MIT. It adds 29 tokens to every session and 1,607 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 2026-09-03.
Other commands, from other repositories
atomic-help
Route a lost user to the right atomic verb, skill, agent, or binary subcommand. Bare invocation reads git state and recommends one next step. Topic keyword or freeform intent → focused pointer. tour → guided walkthrough of the system. Help router, not duplicated docs.
report-issue
Open a atomic GitHub issue via gh. Bug report or feature request — auto-detect from user's description.
test-integration.en
Run the integration test workflow.
test.en
Run the full project test workflow.
pr-ready
Run the project's pre-commit review loop to determine whether the current branch is ready to push — lint, tests, parallel pr-review-toolkit agents plus an over-engineering audit, fix-and-re-run until convergence.
test
Run the project test suite and triage any failures.