Ask for “some ideas for our team offsite” and you might get four ideas or fifteen, a sentence each or a page each. Run the same prompt tomorrow and the size changes again. Without a size, length is the model’s choice.
A size does more than control length. It sets priorities. “The five most common complaints” means find the five that matter and drop the rest. “What customers complained about” means list everything, in no particular order of importance. A number makes the model choose, and choosing is usually the work you wanted done.
Give me some ideas for our team offsite.
Give me five ideas for a one-day offsite for our operations team of 14 people, each in two sentences with a rough cost per person, all under $80 per person.
Numbers replace “some”: five ideas of two sentences each, and the team size and budget give the model facts to plan around.
Numbers beat adjectives
Words like short and brief mean different things to every reader, and to the same model on different days. A number means one thing. Size comes in a few kinds:
- Length: “under 150 words”, “one paragraph”, “fits on one slide”.
- Count: “three options”, “the top five risks”, “ten subject lines”.
- Time: “a 5-minute talk”, “an agenda for a 30-minute meeting”.
- Depth: “a high-level overview for someone new to the project” or “a detailed walkthrough of each step”.
Sizes work for meetings and documents too. “An agenda for a 45-minute meeting, with a time next to each item” gets you timings you can check add up, where “an agenda for the meeting” gets whatever length the model picks.
Word limits are approximate. A model asked for 100 words may give you 85 or 120, so leave yourself some room. If a limit is strict, ask for a number of sentences or bullets, which are easier to hit, and check the result before you send it.
Say what to keep when space runs out
For a short answer, say what it must contain and what to cut first. OpenAI’s guidance suggests exactly this in place of a blanket request for brevity. “Under 100 words. It must include the new date and who to contact; cut the background first” tells the model which sentences to drop.
The same goes the other way. Some models keep answers short by default: Google’s guidance notes that Gemini 3 answers tersely unless you ask for more. If you want depth, ask for it by size: “a detailed answer of about 400 words, with an example for each step.”
If you use a model through an API, output usually costs more per token than input, so a size is also the simplest cost control. The guide to what an LLM call costs has the numbers, and the set a length pattern has more phrasings.
When you are not sure what size you need, ask for less. It is quicker to ask for more detail on two points than to cut a page down to what matters.
Your turn
You manage operations. Your director must decide by Friday whether to renew a software vendor’s contract, and reads everything on a phone.
Done when your prompt covers what to make, who it's for, background facts and length, and scores 4 or more out of 10. Edit the prompt below; the score changes as you type.
A hint
Give the summary a size in numbers, and say what it must cover if space runs short.
Show one good answer
Summarize the attached vendor contract for my director, who has to decide by Friday whether we renew. They will read it on a phone, so keep it under 120 words: the three terms that matter most for renewal (price, notice period and auto-renewal), one sentence each, then one sentence on anything unusual.
It scores 4 out of 10. Yours does not need to look like it: any prompt that passes is right.
More practice
The same idea in 2 other kinds of work. Each one is scored the same way, and each is saved in this browser once it passes.
Practice 1
You run email marketing for an online plant shop. The spring sale runs April 3 to April 6, with 25% off all pots. Most subscribers open emails on their phones, where long subject lines get cut off.
Done when your prompt covers what to make, who it's for, background facts and length, and scores 4 or more out of 10. Edit the prompt below; the score changes as you type.
A hint
Say how many you want and how long each one can be, in numbers.
Show one good answer
Come up with ten subject lines for our spring sale email. The sale runs April 3 to April 6 with 25% off all pots, and it goes to our subscribers, who mostly read on their phones. Keep each subject line under 40 characters so it isn't cut off, and put the discount in the first few words.
It scores 5 out of 10. Yours does not need to look like it: any prompt that passes is right.
Practice 2
You are hiring a shift lead for a warehouse night team. The hiring manager will use your questions in a 30-minute phone screen and wants to learn how candidates handle late deliveries and short-staffed shifts.
Done when your prompt covers what to make, who it's for, background facts and length, and scores 4 or more out of 10. Edit the prompt below; the score changes as you type.
A hint
Give the list a size in numbers: how many questions, and how long the screen runs.
Show one good answer
Suggest six interview questions for a warehouse shift lead on our night team, which works 10pm to 6am. The hiring manager will use them in a 30-minute phone screen to see how candidates handle late deliveries and short-staffed shifts. Give three questions on each topic, one sentence each, with the strongest question first.
It scores 4 out of 10. Yours does not need to look like it: any prompt that passes is right.
Quick check
3 questions. Pick an answer to see whether it is right, and why.
-
Which prompt gives the answer a size the model can hit?
Five ideas of two sentences each means one thing. “Short” and “briefly” mean different things to every reader, and to the same model on different days.
-
Why does “the five most common complaints” often get a better answer than “what customers complained about”?
A size sets priorities as well as length. Asked for five, the model has to rank and choose, which is usually the work you wanted. Short on its own is not the same as accurate.
-
You need a summary under 100 words that must include the new date and who to contact. What else does the lesson suggest you add?
Saying what must stay and what to cut first tells the model which sentences to drop. Capitals do not change the size, and word counts are approximate anyway, so leave yourself some room.
Remember. Give the size as a number; it controls the length and makes the model choose what matters most.