92516 chars, semantic headings (1 H1 + 11 H2s + 48 H3s), 23.3% content ratio

Site accessible to 6 AI agent user-agents

No meta-refresh stubs, JavaScript-redirect stubs, or cross-domain hops across 6 checked pages

All 5 sampled pages are publicly readable (1 with substantive content)

Canonical URL serves text/markdown and text/html via Accept negotiation with Vary: Accept

Nonexistent paths return HTTP 404 with markdown guidance for agents - the strongest 404 contract

Valid sitemap found at https://good-css.com/sitemap.xml with 51 entries

Rich JSON-LD identity: Article with name, description, url, and author/datePublished (1 block)

All metadata signals present: canonical URL, lang="en", og:image, og:type

All trust anchor pages verified: About, Contact, Privacy

All 7 measured pages fit an agent context budget (largest ~24K tokens)

RFC 8288 Link header advertises: sitemap, describedby, alternate(markdown)

Full markdown fallback support. Homepage (https://good-css.com/index.md) and all 1 sampled content pages return markdown: https://good-css.com/specimen/cross-document-view-transitions.md

100% of 51 sampled sitemap entries carry lastmod; newest is 1 day(s) old

Found the llms.txt at https://good-css.com/llms.txt.

The llms.txt is well-formatted: 84 lines with markdown links, 15,546 characters in total.

When-to-use guidance found in llms.txt

All 5 probed llms.txt links resolve to real content

Markdown alternate advertised and verified: https://good-css.com/index.md serves markdown

Frontmatter with title + description, canonical, and last-updated on /index.md

Code fences balanced across 1 markdown document

Developer-related links found on homepage

Path-suffix markdown docs served with text/markdown content-type: /index.md

Server HTML is a well-structured document (main=true, landmarks=4/4, h1=1, maxHeadingSkip=1).

495 native controls, 0 non-native div-soup affordances (100% native).

495/495 interactive elements have a computable accessible name (100%).

No hidden instruction text detected in accessibility-tree attributes or off-screen content.