APIs outlive the applications that first consumed them. Design with that in mind.
Be consistent above all else
Naming conventions, error formats, and pagination patterns should be uniform across every endpoint. Consistency is kindness to consumers.
Version from the start
Breaking changes are inevitable. Having a versioning strategy from day one means you can evolve your API without breaking clients.
Document as you build
OpenAPI specs and clear examples aren’t an afterthought, they’re part of the deliverable.