Have you had to describe requirements for backend, frontend, mobile app, and website?

Yes, I have had to. When describing backend requirements, it is important to clearly define business logic, API interfaces, data formats, and error handling scenarios. For the frontend, user interfaces, interactions, data validation, and component behavior are described. Mobile applications require consideration of platform specifics (iOS, Android), responsiveness, network operation, and device limitations. For websites, cross-browser compatibility, SEO, performance, and navigation ease are important. Usually, requirements are formed considering the specifics of each part, but at the same time, consistency and integration between them are ensured.