The web page does not load for me (I cannot reach the server), but the idea to serve Markdown according to the Accept header is possible, although it might be better to do that by changing the file name and adding a header (or a <meta> command) to indicate this possibility, so that there is a different file name in each case. Some already do this, allowing to change the file name for JSON or Markdown instead of HTML, and is helpful (there are also other common ways that you can change a URL to access it differently e.g. "blob" to "raw" in a git viewer, and I use these things sometimes). However, the reason should not be mainly for AI agents, even if it can be helpful for that purpose too.