"price": "$14.50" can stop Google from reading your product price, one trailing comma makes the whole block unreadable, and a type spelled "Organisation" is simply ignored. This skill finds those and ten other structured data mistakes in your pages and templates before you publish, and explains each fix in plain words, so marketing and SEO teams can act on it without reading code.

Your agent runs a scanner on the schema.org JSON-LD in your HTML pages, page templates (Shopify Liquid, Jinja and Django, Nunjucks, Handlebars, ERB, EJS, Twig, PHP and Blade, Hugo and Go templates, Vue, Svelte and Astro) and .jsonld files. It follows Google Search Central's documentation for each rich result type as of November 2026, understands @graph, lists of items, items with several types, @id references and offers nested inside products, and treats template placeholders such as {{ product.title }} as unknown values, not mistakes. It is plain about features Google has retired: FAQ rich results stopped in May 2026 and How-to results in 2023, so it tells you that instead of promising them. It never fetches a page or contacts Google. It returns BLOCK, REVIEW, or NOT FLAGGED, with the file, line, reason, and a safer approach.

What it checks

BLOCK (fix before shipping)

• J01: JSON that will not parse (trailing or missing commas, single quotes, comments)

• J02: properties Google requires for Product, Offer, AggregateOffer, Review, AggregateRating, BreadcrumbList items, Event, LocalBusiness, Recipe, JobPosting, VideoObject and SoftwareApplication rich results

• J03: JSON-LD in a script with the wrong type, such as application/json

• J04: schema.org items without @context

• J05: misspelled or wrongly capitalized types (Organisation, product, Website) and items without @type

REVIEW (check before release)

• J11: missing recommended properties (image, brand, priceCurrency, availability, author, dates, logo and more) and one-crumb breadcrumbs outside the home page

• J12: prices with currency signs, letters or thousands separators, and currency codes that are not ISO 4217

• J13: dates, durations and opening hours not in ISO 8601, including P30M written for 30 minutes

• J14: relative URLs, localhost or staging URLs, and example.com placeholders

• J15: ratings outside their scale, comma decimals and zero review counts

• J16: values outside Google's lists (availability, itemCondition, eventStatus, employmentType, dayOfWeek, app category)

• J17: markup for rich results Google no longer shows or does not show in that case (FAQ, How-to, online-only events, review stars a business gives itself)

• J18: a non-standard @context such as "schema.org" without https://

What's included

• The scanner (Python 3.9+, standard library only)

• A rules guide with the reason and safer approach for each rule

• A risky and a safe example website (a small coffee shop with product, blog, recipe, event, job and cafe pages, plus a Shopify Liquid template), and the real report the scanner produces on the risky one

Limits

It reads the markup as written in your files: JSON-LD built by code at run time (React or Next.js components, plugins, tag managers, theme filters), Microdata and RDFa are not checked, and it does not compare the markup with the visible page or check that URLs and images work. NOT FLAGGED is not a guarantee of rich results; test the published page with Google's Rich Results Test.

Contents

One ZIP file with 29 files: SKILL.md, the scanner in scripts/ (5 Python files), references/rules.md (every rule with its reason and safer approach), and examples/ (21 example files plus report.md, the real scanner output on the risky example).

How to use: This is an agent skill: a folder with a SKILL.md file and Python scripts that an AI coding agent such as Claude Code, Cursor, or Codex CLI can run. Unzip it into your agent's skills folder (for Claude Code: ~/.claude/skills/), then ask your agent to check your project. The scripts also run on their own with Python 3.9 or newer, with nothing to install. They read your files only: no network access, and nothing is sent anywhere.