Summary
A walkthrough of the RFC 7807 replacement — the type, title, status, detail and instance members, how extension members work, and what it means to treat problem types as part of the public API contract.
RFC 9457: Problem Details for HTTP APIs
Highlights
The five core members
type identifies the problem class as a URI reference, title is a stable human summary, status duplicates the HTTP code, detail explains this occurrence, and instance identifies this occurrence.
Extension members carry the structure
Problem-specific data — a field name, a quota ceiling, a retry hint — travels in extension members, and consumers are required to ignore members they do not recognise.
Problem types are public contract
One type per distinct failure class, no internal identifiers in detail, and treat renaming a type URI as a breaking change to the API.