jimbocoin on Nostr: Yeah, tag filters specifically are single letters, provided the relay supports ...

Yeah, tag filters specifically are single letters, provided the relay supports NIP-12. https://github.com/nostr-protocol/nips/blob/master/12.md

NIP-50 allows a more general ‘search’ filter property for general text searches. https://github.com/nostr-protocol/nips/blob/master/50.md