An API contract defines request and response shapes, behavior, errors, versioning, and expectations between systems.
Good API contracts make developer experience, reliability, and product evolution easier to manage.
A payments API should clearly define idempotency behavior so clients can retry safely without double-charging customers.
Public previews show the map. The app gives you reps, Hatch follow-ups, FLOW feedback, weak-move drills, and saved proof of progress.