For documentation sites, llms.txt acts like a sitemap written for AI. Instead of forcing a crawler to infer structure from navigation and HTML, it lists the pages that matter, with short descriptions, in a format language models parse easily.
The proposal also includes llms-full.txt, a single file containing the full text of the docs in markdown. That gives an AI assistant the entire documentation set in one fetch, without HTML boilerplate, navigation, or scripts.
llms.txt is an emerging convention, not a ratified standard. Publishing it does not guarantee that a particular AI tool will fetch or use it. Check the behavior of the tools your audience uses.