Does adding an llms.txt file do anything?

An llms.txt file is a proposed convention: a plain file at the root of your site describing your content for language models, roughly in the spirit of the robots file that search crawlers read.

The honest position

We have not seen credible evidence that publishing one changes assistant answers, and the major assistant vendors have not committed to consuming it. It costs almost nothing to add, so we are not going to tell anyone to remove theirs. But it should not be counted as work done on visibility, and if a supplier lists it as a deliverable you are entitled to ask what measured change followed.

Why this question keeps coming up

Because it is the shape of thing this industry likes: a concrete, cheap, technical action with a satisfying name, in a field where most real work is slow and involves other people's websites. The demand for a simple lever is genuine. That does not make the lever connected to anything.

What to do instead with the same afternoon

• Check that your product pages state the facts buyers actually ask about, in the words they use, and that nothing on them contradicts your retailer listings.
• Find the two or three third-party pages that keep appearing in your category's answers and check what they say about you. Outdated specifications on somebody else's page are common and correctable.
• Take a baseline reading, so that whatever you do next can be judged.

If the convention is widely adopted and evidence appears that it changes answers, we will say so and change this page. Until then this is what the evidence supports, which is less than the industry would like.