Clarity respects the difference between something being brief and something being incomplete.

Short and unfinished are not the same thing, though they look alike on the page. A brief answer can contain everything the other person needs. An incomplete one leaves out the part they will trip over, and the difference is decided by what they have to do next. Brevity that saves your time and costs theirs is not economy. The test is whether they can act without coming back.

Before sending something short, ask what the reader must do next and whether they now can. Add the one missing sentence rather than three explanatory paragraphs.