Why AI writes long by default
Models are tuned to be polite, thorough and “safe”: they explain, add caveats, summarise and offer help. If you do not say how much you need, they choose the length themselves, and it is usually more than you need at work. A vague prompt also increases the answer: the model adds everything that might be useful. So length and format should be stated directly, the way you would explain a task to a colleague: how much, in what form and for what.
Rule one: set an exact limit
The simplest way is to state the size. “Answer in one sentence”, “no more than 50 words”, “three items of ten words each”. Numbers work better than “briefly”: everyone understands “briefly” differently. For important tasks, add what you do not want to see: “no introduction or conclusion”, “do not repeat the question”. If you must fit a platform limit, such as message or headline length, give the exact number of characters and ask for a length check. AI sometimes miscounts, so check important limits yourself.
Rule two: conclusion first, details after
Ask it to start with the main thing: the answer or recommendation in one sentence, then, if needed, two or three explanations. This format is easy to read: you see the result at once and decide whether you need details. Add who the answer is for: “for a manager who reads in a minute” or “for a client with no technical background”. The audience strongly affects density. Another working technique: ask for a short version first and request details only when needed. That way you control the size instead of wading through extras.
Rule three: shorten iteratively
If the answer is still long, do not rewrite it yourself. Write: “Cut by half, keep all figures and names” or “Keep only what requires action from me”. You can show a sample of the desired length and style. Ask it to remove introductory phrases, repetition and general reasoning. If the AI cuts too much and loses meaning, state what must remain. A few short edits are usually faster than one perfect prompt.
Ready phrases for brevity
Save a few templates and add them to the end of a prompt. “Answer in three points, each no longer than 12 words.” “Only the answer, no explanations.” “Conclusion first in one sentence, then no more than two reasons.” “Explain for a busy person, no jargon.” “If it can be answered yes or no, start with that.” These phrases are universal and fit messaging, analysis and reports. Over time you will notice that a well-set limit does not make the answer worse; it makes it more useful, because the AI is forced to pick the main thing.