AI answers are a second search results page, and most sites are invisible on it
When someone asks ChatGPT, Gemini, Perplexity or Google's AI Overviews for a recommendation, the model assembles an answer from pages it can fetch, parse and trust. That is a different funnel to blue-link search. A page can rank respectably in Google and still never be quoted in an AI answer, usually for mechanical reasons: the content only appears after JavaScript runs, the page blocks AI crawlers in robots.txt, there is no clear factual statement to lift, or the site offers nothing that establishes who is talking.
The checker looks at the things that decide whether a model can use you: whether meaningful content exists in the raw HTML, whether AI crawler user agents are allowed, whether structured data describes the page, and whether headings pose and answer real questions.