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 oaustegard/claude-skills --skill declaring-invariantsgit clone --depth 1 https://github.com/oaustegard/claude-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/oaustegard/claude-skills/declaring-invariants)<a href="https://agentmods.dev/skills/oaustegard/claude-skills/declaring-invariants"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/declaring-invariants/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/oaustegard/claude-skills/declaring-invariants"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/declaring-invariants.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 | $0.00175 | $0.03600 |
| Opus 5.5 | $0.00070 | $0.01440 |
| Sonnet 5.5 | $0.00035 | $0.00720 |
| Haiku 4.5 | $0.00017 | $0.00360 |
Grade A, and why
declaring-invariants 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 — 274 lines — stays where its author put it; the contents beside it link to each section on GitHub.
declaring-invariants
Two scripts over one idea: a test that enumerates a domain must loop the registry rather than a copy of it. Someone also has to say which domains matter in the first place.
python3 scripts/totality_lint.py <repo> # tests that copy a domain
python3 scripts/claims.py <repo> # what the repo declares, and what backs it
Python only, stdlib ast only: no install, no config file, no network.
The failure it catches
A test that loops a hand-written list passes its runner and proves nothing about completeness. When the same members also exist as a registry in the source, the list is a copy, and the copy drifts the moment someone adds a member to the registry and not to the test. Nothing goes red.
Measured on oaustegard/remex, 2026-08-24: adding a fourth member to
ROTATION_CODES with no construction behind it left the entire 267-test
suite green. Four separate tests looked total; each parametrized
["haar", "rht"] against a three-member registry. Only a test that looped the
registry itself caught it.
Adapted from the meta-oracle in daniloc/coherence
(src/oracle-domain.ts), which classifies an oracle's iteration root as LIVE
or LITERAL by parsing the oracle's own AST. That harness needs spec files, a
claim grammar, a ledger and Node; the check does not.
totality_lint.py — tests that copy a domain
| finding | meaning |
|---|---|
sampled-domain |
a parametrize or for over a literal whose members are a strict subset of a source registry. The uncovered members are named. |
ratchet-broken |
a hand-list marked ratchet names a member the registry no longer contains. Detected statically, without running anything. |
unratcheted |
a registry enumerated live with nothing pinning its membership. Suppressed when no-floor already claimed the same line. |
no-floor |
a test iterates a live registry with no len(...) >= n assertion in the file, so an emptied registry passes vacuously. |
stale-ack |
an acknowledgement on a test that now covers the whole domain. |
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 · 274 lines · 175 tokens per session scan A 34d9da0e1e2a
declaring-invariants is a skill published in the GitHub repository oaustegard/claude-skills (157 stars, last pushed yesterday), licensed MIT. It adds 175 tokens to every session and 3,600 once invoked, about $0.0007 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 2026-08-30.
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