Lesson 2.3: Controlling format, tone and reading level

Learn to control the length, structure, voice and reading level of a reply so it is ready to use, with a readability formula and a reusable style sheet.

By the end of this lesson you will be able to specify the length, layout and voice of a reply so that it needs little editing, choose between prose, bullets, tables and numbered steps for the job at hand, measure how readable a piece of writing is with a simple formula, and write a short style sheet that keeps your tone consistent across documents and people. You will adapt one message for three audiences, and you will see why asking for a word count is less reliable than asking for a structure. You should have read Lessons 1.3 and 2.1, since format and tone are two of the parts of a prompt, and a pasted sample is the best way to fix both. No technical background is needed.

A correct answer in the wrong shape is a half-finished job. A paragraph of dense prose when you needed a table, a chatty tone in a note to a regulator, a ten-bullet list when your reader has thirty seconds: each costs editing time and often gets sent anyway because there was no time to fix it. Format and tone are the cheapest things to control in a prompt, because models follow clear instructions about them well, and so they repay attention.

Format: the shape of the answer

Format has four parts, and it helps to decide each deliberately. Part · Examples of what to specifyLength · "Under 120 words", "three sentences", "one page" Structure · Prose, bullets, numbered steps, a table, headings Layout details · Column names, the order of sections, a subject line, a sign-off Cleanliness · "Output only the email, with no introduction", plain text with no symbols ### Length: ask for structure, not just word counts

Models are poor at counting words. Asked for "exactly 100 words", they may return 85 or 130. They are far better at following structure. So control length mainly through the number of parts: "three bullet points, each under 20 words", "two short paragraphs", "one sentence for the headline and two for the detail". Use a word limit as a guard rail, and allow a tolerance: "about 100 words, and no more than 120". Goal · Weaker way to say it · Stronger wayA tight summary · "Make it 100 words" · "Three bullets, each at most 25 words" A short email · "Keep it short" · "Four sentences: greeting, the issue, the request, the thanks" A readable report · "Not too long" · "Five sections of at most two short paragraphs each" A headline · "Catchy" · "A headline of at most eight words with no punctuation" If the answer comes back too long, do not just say "shorter". Give the target: "Cut this to three bullets of 20 words or fewer, keeping the date and the amount."

Predict first: you need a reply you can paste directly into a spreadsheet, with one row for each of ten customers and the columns Name, Issue and Priority. A model's usual habit is to add an introduction and use bullet points. What will you add to the prompt so that the reply pastes cleanly? Decide before reading on.

You will want to name the exact columns and separator, ask for a table or tab-separated lines, and add "output only the table, with no introduction or closing remarks". Naming the columns fixes the structure. The "output only" line removes the friendly opening sentence that would otherwise land in cell A1.

Choosing a structure

Different shapes suit different jobs. A short guide: Shape · Use it when · Avoid it whenProse paragraphs · Explaining reasoning, telling a story, writing a letter · The reader needs to scan or compare Bullets · Listing parallel items, summarising points · The points depend on each other and need connecting words Numbered steps · Instructions where order matters · The order does not matter Tables · Comparing items on the same attributes, or data going into a sheet · There are only two items or the content is narrative Headings · Longer documents the reader will navigate · A short note A one-line answer, then detail · A busy reader who needs the answer first · A reader who needs the argument built up The last row is a good default for work. Ask for the answer first, then the support: "Start with a one-sentence recommendation, then give three reasons." Busy readers get what they need in the first line, and the rest is available to those who want it.

Layout details and clean output

Be specific about the small things that decide whether a reply is ready. If it is an email, ask for a subject line of a stated length, a greeting by name and a sign-off. If it is for a slide, ask for a title of at most seven words and three bullets of at most twelve. If you are pasting into an email program or a chat tool, ask for plain text with no markdown symbols, because asterisks and hash signs that looked like bold and headings in the assistant appear as stray symbols elsewhere. If you want something to copy easily, such as a block of code, a template or a message, ask for it inside a clearly marked block.

text Write the email below. Output only the email: a subject line (at most 8 words), a greeting using the first name, three short paragraphs, and a sign-off with my name. Use plain text with no bullet symbols, bold or headings.

Tone: the voice of the answer

Tone is how something sounds, and it carries meaning of its own. The same facts in a curt tone and a warm tone land quite differently with a customer. Describing tone is harder than describing format, because words like "professional" mean different things to different people, as Lesson 1.2 showed. It helps to think of tone as a few separate dials. Dial · One end · Other end · A concrete markerFormality · Casual · Formal · Contractions, first names, slang against "Dear Sir", full sentences Warmth · Neutral · Warm · Thanks, empathy, "I understand" against facts only Directness · Diplomatic · Blunt · Softening phrases against "do X by Friday" Confidence · Tentative · Assertive · "might", "perhaps" against "will", "must" Energy · Calm · Enthusiastic · Exclamation marks and superlatives against measured statements Instead of one vague word, set two or three dials and add a concrete marker. Compare "Write in a professional tone" with "Formal, warm and direct: full sentences, no contractions, one line of thanks, and a clear request with a date". The second can be followed, and checked.

Show the voice you want

As with format, the best way to fix tone is a sample. Paste two short pieces you like, written in the voice you want, and say "Match the tone and sentence length of these. Do not reuse their wording." Or paste your own earlier email as the model. A few lines of your actual writing teach more about your voice than a paragraph of adjectives. You can also describe the reader: "The reader is a senior manager who dislikes jargon and has two minutes." The reader's needs imply a tone.

A style sheet in five lines

If you write often for the same organisation, capture the voice once as a style sheet and paste it into prompts. Five lines are enough to begin.

text Voice: clear, warm and direct, like a helpful senior colleague. Sentences: short, usually under 20 words. Prefer active verbs. Words: plain English. No jargon without a one-line explanation. Avoid "leverage", "synergy", "utilise" and "reach out". Do: address people by first name, say what happens next, give dates. Do not: use exclamation marks, promise outcomes we cannot guarantee, or blame the customer.

A shared style sheet means that a team of five, each using an assistant, produces text that sounds as though one person wrote it. Update it when you spot a recurring problem, such as the assistant overusing a phrase.

Reading level

Plain writing is not dumbed-down writing. It is writing that the reader can follow at the speed they read. A simple, widely used measure is the Flesch reading ease score, which depends on two things: how long the sentences are and how long the words are.

reading ease = 206.835 − 1.015 × (words per sentence) − 84.6 × (syllables per word)

Higher scores are easier. A text averaging 18 words per sentence and 1.6 syllables per word scores 206.835 − 18.27 − 135.36 = 53.2, which falls in the "fairly difficult" band. Shorten the sentences to 12 words and the words to 1.4 syllables, and the score becomes 206.835 − 12.18 − 118.44 = 76.2, "fairly easy". The formula is a rough guide, and it does not capture clarity or jargon, but it is a useful check on a long reply, and many word processors compute it for you.

To control reading level in a prompt, say so directly and give a measurable target: "Aim for sentences under 15 words and everyday words a school student would know", or "Write for a reader with no finance background." Then check the result. If it comes back stiff, ask: "Rewrite this with shorter sentences and simpler words, keeping every fact."

Why shorter is a kindness

Length is a cost placed on the reader, and the cost multiplies by the number of readers. Take a 600-word reply that goes to 50 colleagues. At a typical reading speed of about 230 words a minute, each person spends about 2.6 minutes, and together they spend about 130 minutes. A 200-word version takes each reader under a minute, and the group spends about 43 minutes. The shorter version saves roughly 87 minutes of other people's time, and it is more likely to be read in full.

Shortening does not mean removing the substance. It means putting the answer first, cutting repetition and choosing one clear ask. Asking an assistant to "cut by half, keeping the decision, the owner and the deadline" works better than "make it shorter".

One message, three audiences

The same facts often need to reach several readers in different voices. Take a payments outage that lasted forty minutes, affected about 3,000 customers and was caused by a failed update that has been reversed. A single prompt can produce all three versions if you specify each reader.

text Using only the facts below, write three versions of a message about the outage.

Facts: a payments outage lasted 40 minutes on 29 October 2026; about 3,000 customers could not complete payments; the cause was a failed software update, now reversed; no money was lost; a review will be finished by 5 November.

1. For customers: 60 words, warm and plain, apologise once, say what to do if a payment failed. 2. For staff: 80 words, factual, include what to tell customers who call. 3. For the board: 50 words, formal, include scale, cause, impact and next steps.

The facts stay fixed and the tone, length and emphasis change. The customer version leads with an apology and an instruction. The staff version leads with the script. The board version leads with scale and cause. Ask for all three together and you can see at a glance that the facts match. Then verify them against your source, because each rewrite is another chance for a number to drift.

Delicate tone: bad news, apologies and complaints

The hardest tone to get right is the one for bad news. Left alone, assistants lean towards effusive apologies and empty reassurance. A few instructions help.

Apologise once, specifically. "We are sorry that your payment failed on 29 October" beats three paragraphs of regret. Do not over-promise. Add "do not promise outcomes or timelines that are not in the facts." Avoid stock phrases. Ban "we value your feedback" and "your call is important to us", which readers hear as filler. Say what happens next, and by when. Concrete next steps rebuild trust faster than sympathy. Keep blame out. "Do not blame the customer or any named person."

Where a message is sensitive or legal, have a person review it, whatever the tone looks like. And if you work in more than one language, have a fluent reader check the tone of the translation, because politeness conventions differ between languages, and a literal translation of an English tone can sound too curt or too grovelling.

Worked examples

Example 1: a weekly update. A project lead wants a status note for twelve stakeholders. The prompt asks for: a subject line of at most eight words, a one-sentence headline stating overall status as green, amber or red, three bullets (done, next, risks) of at most 20 words each, and "plain text, no symbols". The result is the same shape every week, which makes the notes easy to scan and compare.

Example 2: a customer reply in the company voice. A support agent pastes the style sheet, two past replies she is proud of, and the customer's complaint in fences. The instruction: "Reply in this voice, under 100 words, apologise once, say what we will do and by when. Do not offer compensation." The reply matches the house tone and avoids the unwanted promise.

Example 3: a table for a spreadsheet. An analyst needs ten interview notes sorted into themes. The prompt specifies the columns Theme, Quote and Count, asks for tab-separated lines and adds "output only the table". The result pastes cleanly, and the analyst spends the saved time checking that the quotes are real.

Common mistakes

Asking for an exact word count. Ask for a structure and a limit with tolerance. Letting the model choose the shape. Say bullets, table or prose, and say why it suits the reader. A single vague tone word. Set two or three dials with concrete markers, and show a sample. Pasting markdown into an email. Ask for plain text when the destination is not a chat window. Forgetting the introduction. Add "output only the email" or "output only the table". Rewriting for tone without rechecking facts. Every rewrite can alter a number or a date. Over-formatting short answers. Not every reply needs headings and bullets. Ignoring the reader's time. Put the answer first and cut what does not change a decision.

Key takeaways

Format has four parts: length, structure, layout details and cleanliness. Naming each makes a reply ready to use. Models count words poorly but follow structure well, so control length by the number and size of parts, and use a word limit with a tolerance. Put the answer first, then the support. Match the shape to the job: prose, bullets, steps, a table or headings. Tone is several dials, not one word. Set two or three with concrete markers and show a sample. A five-line style sheet keeps a team consistent. Reading ease depends on sentence and word length. Plain business writing aims for about 60 to 70 or higher. Shorter messages save the reader's time, multiplied by the number of readers. Re-verify facts after any rewrite for tone.

Check yourself

1. Why ask for "three bullets of at most 20 words" instead of "exactly 60 words"? Models count words unreliably but follow structure well, so controlling the number and size of parts is more dependable. 2. What does "output only the table, with no introduction" prevent? The friendly opening sentence that would land in the first cell when you paste. 3. Name three tone dials and a concrete marker for one of them. Formality, warmth, directness, confidence or energy. For example, formality shows in contractions and first names against "Dear Sir" and full sentences. 4. A text has 15 words per sentence and 1.5 syllables per word. What is its reading ease? 206.835 − 15.225 − 126.9 = 64.7, which is plain English. 5. A 400-word message goes to 30 people reading at 200 words a minute. What does a 150-word version save in total? (400 − 150) ÷ 200 × 30 = 37.5 minutes.

Try this

You need an assistant and about forty minutes.

1. Choose a message you write regularly, such as a weekly update or a customer reply. Collect two past examples that you like. 2. Write a five-line style sheet for the voice. Include voice, sentence length, words to use and avoid, and two do's and don'ts. 3. Write a prompt with your facts in fences, the style sheet, the format (length by structure, plain text, output only) and a sample. Run it in a fresh chat. 4. Ask for three audience versions of the same facts. Compare facts across the three, and mark any that changed. 5. Measure the reading ease of the first reply, using the simulator with your sentence and syllable counts, or your word processor. Ask for a rewrite aimed at 65 or above and measure again. 6. Score the replies with this rubric, one point per yes. Check · First reply · After style sheetRight shape for the destination? · · Right tone for the reader? · · Reading ease at your target? · · Facts unchanged from your source? · · Sendable with light edits? · · 7. Calculate what the shorter version saves your readers, using the reading-time simulator.

A good result is a saved style sheet and format block that you reuse, a visible gain on the rubric and a short note on the facts you had to correct. In the next lesson we turn to the most important check of all: how to spot an answer that is fluent and wrong.

Tags: Prompt Engineering Format Tone Readability Style guide