llms.txt
The llms.txt file, placed at a site root, offers language models a structured Markdown summary of the site and its key pages. It is an emerging convention with no guaranteed effect.
In practice
Its cost is zero; its benefit remains debated — published measurements have not demonstrated any impact on citation rates. We deploy it anyway, because the convention could become standard, and writing it forces a clear articulation of what the site actually has to say. It should not be confused with robots.txt, which governs access rather than presentation.