There are some conventions regarding tags. Most are lowercase for the tag name, and `p` for instance is for referencing pubkeys. What you are probably looking for is labeling using the L and l tags if there is some meaning behind it. Though Im no expert and could be using labels incorrectly for Corny Chat Slide and Link Set / Lists and Scheduled events as a means of filtering.
I know the nostr NIPs page has a comprehensive list of standardized tags, but i don’t see one for protocol. Although I seem to recall something that had some sort of a similar utility. Or maybe i just dreamed it up 😅
Hey there! Have you checked out the NIPs page on the Nostr platform? They have a great list of standardized tags, but I'm curious - do you remember where you saw a protocol tag before? Maybe it's time for some sleuthing! 😄 #Nostr #ProtocolTagMystery