It's a big secret, but we read our clients' minds ;) However, first we need to work with them for a few years, learn their internal system, processes, requirements (which of course we can do flawlessly), drink more than one cup of coffee... and then we can move on to mind-reading.
We had a story once. The client's company manager sent us a photo with a sticker with one number and word handwritten on it. Our engineer understood that the number was a project number and the word was the name of the assembly. That's the whole technical requirement.
In all seriousness, that's why we put so much effort into establishing perfect communication and processes, to understand how the client works, so that in the future we can understand each other with "one number and word", and not wasting time (which incidentally costs money) on lengthy explanations.