toFixed(2) is wrong the moment a currency has zero decimal places

Hard-coding two decimal places on every price produces 1000.00 JPY for a yen item that should read 1000 JPY -- a real, checkable Merchant Center rejection, not a cosmetic issue.

This is one of the things Product Feed & Merchant Center Compliance already handles. Get your products into Google Shopping and keep them from being rejected.

Buy for $1292 of 3 clean-room builds passed · full refund if it fails on your machine

Is this you?

Formatting every price with .toFixed(2) works correctly for USD, EUR, and most currencies an agent is likely to test against -- and produces a malformed price string the moment the catalogue includes a currency like JPY, which uses zero decimal places, turning a clean integer amount into a value Google's price-format check flags as invalid.

Why this one is easy to get wrong

Two decimal places is the default mental model for "money" in most software, reinforced by testing almost exclusively against USD-priced fixtures -- there's no error locally, because .toFixed(2) never throws, it just silently produces a technically-wrong-but-plausible-looking string for the one currency that needed different treatment.

What you get instead

minorUnitDigits() reads the correct fraction-digit count straight from Intl.NumberFormat(...).resolvedOptions().maximumFractionDigits -- JPY resolves to 0, USD to 2 -- so formatAmount() and formatPrice() are correct for every currency the Intl runtime knows about, with no hand-maintained currency table anywhere in the pack. formatPrice is also the single function allowed to emit a price string at all, so there's exactly one place this rule could ever be applied inconsistently.

Source: ARCHITECTURE.md 'Money' — checkable in the pack you receive

How you actually use this

You don’t install a library or wire up an SDK. Your own coding agent builds the code in your project, and you keep it — no runtime dependency on us.

Step 1
Download and unzip
You get a folder: the docs that tell an agent what to build, a starting skeleton, and the test suite that decides when it's done.
Step 2
Open it in Claude Code or Cursor
Point your coding agent at the folder. Nothing to install, no account with us, no API key.
Step 3
Paste one prompt
The pack contains the exact prompt. Paste it as your first message and leave it alone — it works through the build itself, choosing a cheaper or stronger model per task.
Step 4
Run ./verify.sh
One command. It prints a pass or fail for every check. Green means the build is done — the same script we ran to produce the receipt on this page.

Typical build: about 44 minutes of your agent working, mostly unattended. Then you integrate the working module into your app the way you would any code you’d written yourself.

Why you can believe this

2 of 3 runs passed

We ran this pack from an empty folder 3 times and published exactly what happened — every check, the model, the token cost, the wall time. Not a testimonial, and not our opinion: the same verify.sh you run yourself. Read the full receipt →

Buy for $129 14-day refund if verify.sh fails →