You truly know that you're totally out of the loop with some topic when you read "Music discovery on the AT Protocol" and think how the heck did they manage to build such thing with just AT Commands against a GSM modem [^]
^ https://ozeki.hu/p_3653-at-command-guide-for-gsm-modem-netwo...
I don't know why you are being downvoted, but I totally thought about that AT protocol first.
Apparently, the OP refers to <https://atproto.com/> per the FAQ at <https://docs.rocksky.app/faq-918661m0#what-is-the-at-protoco...>