What the documentation says
Google’s guide to optimising for generative AI in Google Search puts it in one sentence. Structured data is not required for generative AI search and there is no special schema.org markup you need to add. The same guide says you do not need to create new machine readable files, AI text files, markup or Markdown to appear in Google Search.
Google’s page on AI features and your website sets the actual entry condition, which is ordinary. A page must be indexed and eligible to be shown in Google Search with a snippet. There are no additional requirements to appear in AI Overviews or AI Mode. Microsoft is similarly careful in the Bing Webmaster Guidelines, where the section on using structured data accurately states that it may support clearer grounding while it does not guarantee visibility or grounding traffic.
The job it genuinely does
There is one thing structured data does that nothing else does, which is state identity in a form a machine does not have to infer. schema.org defines sameAs as the URL of a reference web page that unambiguously indicates the item’s identity. An Organization block with sameAs pointing at your Companies House record, your verified social profiles and a Wikidata item if you have one staples those identities together.
Microsoft asks for exactly this in the same guidelines, under a section about defining entities clearly and consistently. It asks site owners to use clear and consistent naming for people, organisations, products and locations while avoiding ambiguous references. Structured data is the cleanest way to obey that instruction, because you are stating a fact instead of hoping it is inferred from your page copy.
The rules with teeth
Google’s general structured data guidelines are strict about honesty. Do not mark up content that is not visible to readers of the page. Markup must be a true representation of the page content. Breaking that earns a manual action, which removes the page’s eligibility for rich results, although Google says it does not affect ranking in web search.
Microsoft’s guidelines list misleading structured data among the practices to avoid, saying markup that is irrelevant, inaccurate or misleading may be ignored and can affect trust plus eligibility for enhanced features. So the sensible brief is short. Mark up what is on the page, keep the Organization block accurate and spend the rest of the budget on the words a reader would actually quote.