Google reads the HTML your server sent. It does not run your JavaScript.

A checker that renders the page in a headless browser reports a page as fine even when Google's own crawl -- which does not execute JavaScript -- sees no structured data on it at all.

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?

Injecting a product's JSON-LD via client-side JavaScript makes it appear correctly in a browser, in a headless-browser test, and in a rendered preview -- and Google's Merchant Center crawl reads the raw HTML bytes your server returned, without executing any client-side script, so the structured data it actually sees is nothing at all.

Why this one is easy to get wrong

Testing a page by opening it in a browser (or a headless one) and confirming the markup is present passes every check an agent would naturally run, because a browser does execute JavaScript -- the gap only exists between what a browser shows a human and what a non-executing crawler reads off the wire, which isn't a distinction a rendered-page test can expose.

What you get instead

The consistency checker deliberately reads raw server HTML with cheerio, never a rendered DOM, so it sees exactly what Google's crawl sees. hasJsOnlyStructuredData() is a documented heuristic layered on top: no static markup found, but a script body mentions application/ld+json or schema.org -- a different finding, with a different fix, from markup that's simply missing outright. The product page itself renders its JSON-LD server-side for the same reason, quoted directly from the spec's own must_be_in_server_html_note.

Source: ARCHITECTURE.md 'Structured data' — 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 →