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 skills/leifericf/agentic-sdk/check-correctnessnpx skills add leifericf/agentic-sdk --skill check-correctnessgit clone --depth 1 https://github.com/leifericf/agentic-sdkWrote 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/leifericf/agentic-sdk/check-correctness)<a href="https://agentmods.dev/skills/leifericf/agentic-sdk/check-correctness"><img src="https://agentmods.dev/badge/skills/leifericf/agentic-sdk/check-correctness.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 | $0.00028 | $0.00871 |
| Opus 5 | $0.00014 | $0.00436 |
| Sonnet 5 | $0.00006 | $0.00174 |
| Haiku 4.5 | $0.00003 | $0.00087 |
Grade A, and why
check-correctness 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 — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.
check-correctness
Role: review the shard for behavior that is simply wrong.
Failure model: the code does not do what the surrounding system needs on some input or interleaving; the bug that ships is the edge the happy path hides.
Look for
- Arithmetic and indexing. Off-by-one in a loop bound; signed and unsigned mismatch; integer overflow on an accumulator or a size computation; a count flowing into indexing without a bound check; float precision loss in a long-running accumulator; a division whose divisor can be zero.
- nil, null, empty, and boundary inputs. Empty collection, single element, zero, negative, a missing map key, an empty string, an Option or Result unwrapped without the missing case. The happy path is not the test; the boundary is.
- Order and composition sensitivity. A transformation chain that produces a different result when applied in a different order; a filter or reduction that mishandles the empty case; a sort that is not stable where the caller depends on stability; a set versus list confusion that drops or duplicates elements.
- Concurrency and interleaving. A callback that fires mid-mutation; a message that arrives between a decision and its effect; a shared mutable value read and written without the synchronization the shell owns; a future or task awaited in the wrong order. The pure core avoids this by construction; the shell is where it lives.
- Protocol and state machine errors. A case, match, or switch with a missing arm; a state transition that skips an intermediate state the contract requires; an error code outside the documented catalog; a sentinel value stored where the domain expects absence.
- Error-path correctness. A recovery path that swallows the failure and returns a wrong success value; an error mapped to the wrong diagnostic; a cleanup path that skips a step the success path runs.
- Native edge dispatch. A wrapper that calls the wrong native function, passes arguments in the wrong order, or misreads the return shape. The lifetime and ownership of the handle are check-memory's; the dispatch logic is here.
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 First seen · 90 lines · 28 tokens per session scan A 5dabd1e71d7f
check-correctness is a skill published in the GitHub repository leifericf/agentic-sdk (5 stars, last pushed 2d ago), licensed MIT. It adds 28 tokens to every session and 871 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 2026-08-31.
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