The context here might be that we are in a design review - you are presenting a design. Maybe it's verbally, but maybe it's a document. Ideally it's a document

The context here might be that we are in a design review - you are presenting a design. Maybe it's verbally, but maybe it's a document. Ideally it's a document, so you can describe it by writing it down. But if someone asks a hard question that you didn't prepare for, well you still have to make a best effort to answer it verbally. You can use "I'll write down my thoughts and get back to you" to SOME things, but not every time.