What is Swagger/OpenAPI, and why is it important for API design?

Short answer: Swagger/OpenAPI is a specification for defining REST APIs. Provides machine-readable and human-readable documentation. Enables automatic client SDK generation, testing, and validation. Improves team collaboration and consistency in API design.

Real-world example (ShopNest)

ShopNest exposes REST APIs for cart and checkout. Controllers stay thin; business rules live in application services.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.