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 rainmanjam/poka-yoke --skill guardrailsgit clone --depth 1 https://github.com/rainmanjam/poka-yokeWrote 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/rainmanjam/poka-yoke/guardrails)<a href="https://agentmods.dev/skills/rainmanjam/poka-yoke/guardrails"><img src="https://agentmods.dev/badge/skills/rainmanjam/poka-yoke/guardrails/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/rainmanjam/poka-yoke/guardrails"><img src="https://agentmods.dev/badge/skills/rainmanjam/poka-yoke/guardrails.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 | $0.00098 | $0.01738 |
| Opus 5 | $0.00049 | $0.00869 |
| Sonnet 5 | $0.00020 | $0.00348 |
| Haiku 4.5 | $0.00010 | $0.00174 |
Grade A, and why
guardrails 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 12d 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 — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Poka-Yoke Guardrails
Design-time devices protect the code you are writing now. Guardrails protect the code everyone writes later, including the version of you who is in a hurry. They are Shingo's successive check: the next station refuses to accept bad work.
The reason this mode exists as its own thing: the most common failure in software quality is agreeing on a rule and then writing it down. A rule in a wiki has a half-life of about one onboarding. The same rule wired into a gate applies itself and costs nothing to remember.
Building, not reviewing
Most of the time this mode is reached while someone is building the thing, not afterwards. That changes the deliverable. They asked for the config, so produce the config, working, complete, in their stack. Do not hand back a severity table when the person is mid-feature; a list of findings about code they have not written yet is not useful to them.
Then add a short closing note, three or four lines, covering:
- which misuses the shape you chose makes impossible, and at which rung,
- what you left possible on purpose, and why that tradeoff is the right one here.
That closing note is what stops the device being undone in six months by someone who cannot see why it is there. It is also the difference between mistake-proofing and a code generator: the reasoning travels with the code.
When the code already exists and they are asking what is wrong with it, switch to the audit voice, ranked findings with the mistake, the consequence, and the device. Match the mode to where they are in the work, not to this file's default.
Pick the earliest gate that can hold the rule
The same rule can live at several points in the lifecycle. Earlier is better, feedback is faster, cheaper, and lands while the author still has the context in their head. But earlier is also easier to bypass. The resolution is to place the device early and back it with a gate that cannot be skipped.
| Gate | Feedback speed | Bypassable? | Best for |
|---|---|---|---|
| Type system / compiler | instant | no | anything the types can express, always first choice |
| Editor + lint | seconds | yes (ignore comment) | style, banned APIs, unsafe patterns |
| Pre-commit hook | seconds | yes (--no-verify) |
fast checks: secrets, formatting, obvious footguns |
| Pre-push hook | ~a minute | yes | medium checks you don't want to wait for on every commit |
| CI required check | minutes | no, with branch protection | the real enforcement, everything that must not merge |
| Database constraint | instant, at write | no | data invariants, across every service and every script |
| Runtime assertion | at execution | no | invariants no earlier gate can see |
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.
- 12d ago First seen · 132 lines · 98 tokens per session scan A 8106ac1ca777
guardrails is a skill published in the GitHub repository rainmanjam/poka-yoke (22 stars, last pushed 11d ago), licensed MIT. It adds 98 tokens to every session and 1,738 once invoked, about $0.0005 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 2026-08-30.
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