What does an llms.txt actually buy you?

There is no standard behind it in any meaningful sense, no guarantee any assistant reads it, and no way to measure whether it changed anything. By every normal test it is speculative.

The argument for it is a bet, and it should be stated as one: a growing share of product discovery now happens inside an answer rather than a results page, and the cost of being legible to that surface is one static file and an allowlist. Asymmetric enough to be worth taking.

What I do not know — and what nobody claiming expertise here actually knows yet — is whether the file does anything, or whether the visibility comes entirely from the ordinary crawl. I ship it. I do not bill for it as a strategy. I would rather say that out loud than sell a certainty I do not have.