What is the importance of API documentation?

Short answer: Provides clear usage guidelines for developers. Reduces onboarding time for new teams. Ensures consistency across different services. Helps with discoverability of endpoints, parameters, request/response formats. 👉 Tools: Swagger (OpenAPI), Postman, Redoc.

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.