IMHO if you want to do a request-response situation, use REST. The nostr protocol is less than ideal, worse than REST, for this kind of communication. You can use your nostr identity, we have several standards for that over HTTP (blossom and NIP-98).
But also, DVMs are defined very generically, which means they don't interoperate without coming up with much more specific standards. And that is what fiatjaf (npub180c…h6w6) is pushing for in https://github.com/nostr-protocol/nips/pull/1903