Your agent is confident. That is the problem.

Twenty skills that stop a coding agent — or the person running it — doing the wrong thing quickly and certainly. Each one exists because it happened: a real system broke, or a real number went wrong, and the rule is what was left afterwards.

Get the pack $29 once

Instant download. No account, no subscription, nothing renews. — or read one of them in full first, free, with nothing to enter.

An agent that is wrong and hesitant costs you a minute. An agent that is wrong and sure costs you the afternoon, and sometimes the data. Almost every rule in here is about the second kind.

What is in it

a-negative-needs-two-sources	Concluding a thing is absent because one place said nothing
a-rule-in-one-caller-is-not-a-rule	Trusting a rate cap or spend limit only one code path enforces
an-identity-is-not-a-finding	Reporting a ratio that was true by definition
cite-the-document-not-the-digit	Believing a number because it is specific
effective-sample-size	Acting on a result a handful of correlated events produced
kill-or-scale	Judging a venture on thresholds set after seeing the numbers
patch-a-live-system	Editing running code with an anchor that matches twice
prove-it-took-effect	Believing a deploy landed because the page looked right
schema-is-shape-not-truth	Treating validated JSON as verified fact
silent-scheduled-failure	Assuming a loaded cron job is a running one
triage-by-shippability	Ranking findings by severity when none can reach a user
unmask-before-theorising	Theorising about a generic error instead of finding the real one
verify-before-counting	Reporting what a check found without checking the check
zero-cost-preflight	A readiness check that consumes the thing it is checking

And six for the money

An agent that is wrong about a fact costs you an afternoon. One that is wrong about a number costs you the month.

check-the-rail-before-quoting	Naming a price the payment processor cannot charge
the-platform-is-not-the-ledger	Believing the conversion count of the platform you pay
a-trial-is-a-dated-bill	A free trial that started as a side effect and bills in a month
a-threshold-moved-is-a-threshold-gone	Moving a kill rule in the week it falls due
spend-needs-a-payback-not-a-ban	A blanket no-spend rule that rejects without an argument
no-return-path-no-spend	Paying for volume on a channel nobody can reply to

How it works

Twenty SKILL.md files. Copy them into ~/.claude/skills/ for Claude Code, ~/.codex/skills/ for Codex, or point Cursor and OpenCode at the folder. Most agents load one automatically when its description matches what you are doing. There is no code to run, nothing to configure, and nothing phones home.

Who it is not for

If you have not yet had an agent tell you something confidently and wrongly, you will not recognise any of these, and you should not buy it yet. If you have, you will recognise most of them on sight.

One developer, personal or commercial use. These are judgement aids, not guarantees: they tell you what to check, not what is true. Pack version 2026-09-21b.