Google has recently added `llms.txt` to Chrome's Lighthouse check for agentic browsing (https://searchengineland.com/google-llms-txt-chrome-lighthou...), so adoption may be coming. Admittedly, I put more faith in

  <link rel="alternate" type="text/markdown" href="https://example.com/foo.md" title="Markdown version of the &lt;Foo&gt; page">

I have created an `llms.txt` for my website anyhow. I use a fixed LLM prompt to generate it from the internal links in `index.md`.

The same could be said of robots.txt

And anything else that might tell them not to access something.

To be fair, "not adopted by any major AI player" is probably the most web-standard-compliant phase of a new web standard.