Guide
What ‘learns your brand voice’ actually does to your writing
Keep the tool. Give it rules it can fail, and check what comes back.
A writing tool that learns your brand voice from a few samples learns your topics and your favourite phrases, not your rules, so its drafts drift back to the way your whole sector already writes. The median UK accountancy firm writes 3.8% of its sentences at five words or fewer; real voices run between 15% and 29%. Give the tool rules a draft can fail, and test what it writes against them.
The promise is on almost every AI writing tool now: upload five samples and it will write like you. The speed is real, and nothing here argues against it. What the tool does with those samples is worth knowing before you pay for a year of it.
Five samples
What does an AI tool do with your five samples?
Most tools end up holding two things: a short description of how you sound, and a handful of your sentences to imitate. The description is usually adjectives. Clear, confident, warm, professional. The sentences tell it what you talk about and a few phrases you use.
Neither gives it a rule. Five samples cannot say that your median sentence is eleven words, that one sentence in six is short enough to land a point, or which twelve words you never use. Nobody counted, so nothing the tool learned can be failed.
A description it cannot fail is one it already meets.
The pull
Why does the output drift back to the middle?
A language model writes the likeliest next sentence. Likeliest means commonest, and commonest means the way most businesses already write. Your samples nudge it off that line for a paragraph or two. Then the default comes back, because nothing in the brief says it has gone wrong.
The middle is easy to measure. Landing is the share of sentences at five words or fewer, the ones that carry the point after a long sentence has done the explaining. Real voices measured between 15% and 29%. Thirty-one UK accountancy firms have a median of 3.8%, and thirty-five US CPA firms a median of 6.4%. A draft that slides towards its sector slides towards those numbers.
You will not see it in one draft. You see it in the tenth, when every paragraph is three long sentences of nearly equal length and none of them stops to make a point.
Sounding alike
Why does the same tool make you sound like your competitors?
Your competitors can buy the same tool, and its default is the same for every customer. Each firm’s samples pull a little in their own direction. The default pulls everybody the same way, and it usually pulls harder than five samples do.
A sector shares a phrasebook before any tool arrives. In the two accountancy benchmarks, two words turn up on more than half the UK sites measured, and one of them on more than half the US sites. They are counted as firms using them, not as occurrences.
| Word | UK firms | US firms |
|---|---|---|
| journey | 20 of 31 | 14 of 35 |
| excellence | 16 of 31 | 18 of 35 |
A tool that writes the likeliest sentence writes from that phrasebook. A buyer reading three shortlisted sites in one afternoon cannot remember which firm said which, and a fourth written by the same tool will not help them.
Same default. Same phrasebook. Same sentence.
Test it yourself
How can you test any tool’s output yourself?
You need nobody’s word for any of this, including this guide’s. Ask the tool for a page you would normally write yourself, then paste the draft into the free Anyone Test. It scores four things: own words, rhythm, landing and evidence. The scoring runs in your browser, so an unpublished draft never leaves your machine.
Then test what you have already published. Type your web address instead of pasting, and choose your sector under "Compare with your sector" where it is listed. If the tool’s draft scores lower than your own site, the tool is pulling you down, and the sector line shows how far towards the middle. If your own site already sits near the sector median, the samples you gave it were the middle to begin with.
Two scores, two minutes, and you know which way it moved you.
What to give it
What should you give the tool instead?
Rules a draft can fail. A brand voice setting usually asks for a description, words to use, words to avoid and some examples. Fill each one with something a reader could check.
Does nothing
"Clear, confident and approachable, with a warm, professional tone."
Four adjectives, no test. The tool already believes it does all four.
Changes the draft
"Median sentence eleven words, never more than fifty. One sentence in six under five words, placed where the argument turns. Every claim of benefit carries a figure or a named example in the same sentence."
Three rules, and a draft either keeps them or it does not.
- The description. Numbers like the ones above, never adjectives.
- Words to use. Twelve phrases quoted from your own published work.
- Words to avoid. The stock phrases already in your own writing, and the ones your sector reaches for.
- Examples. Worked pairs: a generic sentence beside your version, with one line on what changed.
Writing those rules is the work in how to write brand voice guidelines, and how to measure brand voice covers the counting. A Wordprint does both from your own published words and lays its prompt pack out for exactly those four boxes, with a plain-text copy, so you paste rather than retype.
Before you buy
What three questions should you ask a supplier?
- What exactly did it learn? Ask for the answer in numbers: sentence length, the share of short sentences, the words it will never use. If the answer comes back in adjectives, it learned adjectives.
- Will it give the same answer twice? Upload the same samples on two different days and compare the descriptions. A measurement repeats. An impression drifts.
- How will you know when a draft has drifted? Something has to check each draft against the rules before a customer reads it. If the answer is that you will notice, that something is you.
A good tool can answer all three. Most are never asked.
Keep the tool. Give it rules, and check what it writes.
Test a draft against your own site
Paste a draft from the tool you use, test your website by its address, and compare both with your sector. Each takes about a minute. A Wordprint then writes the rules down, with a prompt pack for the tool you already pay for and the Check to show you when a draft drifts.
More guides: brand voice instructions that bite, how to write brand voice guidelines, how UK accountancy firms sound, how US CPA firms sound.