HTTP signatures 
Standard message payloads
Descriptive error messages

nostr:npub1u27r9h3j9pvrplaffsmpn698e8xhmuqhdgcxldv67ammql9pumnqha3qfq nostr:npub1fmhk33ta7scnlmhdur3xvju4w29qlc0kare9pkqupt2efe4lae8qashpey