How to Create a Brand Voice Guide for AI Writing Tools (Template + Test)

On this page 11

1. What an AI-ready brand voice guide contains
2. Why your normal brand guidelines don't work as AI instructions
3. Before you start: gather your raw material (30 minutes)
4. Step by step: build your brand voice guide
5. Copy-paste brand voice guide template
6. Good vs bad AI output: examples using the guide
7. Where to put your guide in popular AI tools
8. How to test your brand voice guide before your team uses it
9. Keeping your guide working over time
10. Common mistakes to avoid
11. Quick checklist

The short answer

To create a brand voice guide for AI writing tools, write a one-page instruction set that tells the AI who it is writing for, turns your voice adjectives into checkable rules and shows paired good and bad examples. Add hard limits so it never invents prices, statistics or claims. Paste it where the tool keeps standing instructions, such as custom instructions, a project or a custom assistant, then test it on five real tasks before your team relies on it. Even then, review every output: no guide makes AI perfectly consistent.

What an AI-ready brand voice guide contains

A working guide has seven parts:

1. Audience: who reads your content and what they care about.
2. Voice rules: 3 or 4 traits, each turned into concrete do and don't rules.
3. Tone by context: how the voice adjusts for support replies, social posts, sales pages and bad news.
4. Word list: terms to use, terms to avoid, names spelled correctly.
5. Formatting rules: spelling, dates, length, headings, emoji.
6. Good and bad examples: short pairs showing the difference, with a one-line reason.
7. Hard limits: no invented prices, statistics, testimonials or guarantees.

Why your normal brand guidelines don't work as AI instructions

Most brand guidelines were written for designers and new staff. They don't translate well into instructions for an AI.

• Adjectives are too vague. 'Friendly', 'professional' and 'bold' mean different things to different people. When the AI isn't told what you mean, it fills the gap with generic defaults.
• Visual identity doesn't affect writing. Logos, colours and mission statements don't change a single sentence the AI produces.
• Rules and examples beat descriptions. It's widely shared practical advice that AI tools follow concrete rules and imitate examples more reliably than they interpret a description of a personality.
• Long guides get partly ignored. A 30-page brand book full of exceptions and contradictions gives the AI too much to weigh. Short, specific and consistent works better.

The signs of generic AI copy

You probably already know them:

• Inflated openers: 'In today's fast-paced world…'
• Stacked adjectives: 'innovative, seamless, cutting-edge solutions'
• Vague claims: 'we're passionate about delivering excellence'
• Overused words: unlock, elevate, seamless, empower, game-changer
• A pushy close: 'Ready to take your business to the next level? Contact us today!'

A good guide is built to remove exactly these.

Before you start: gather your raw material (30 minutes)

Base the guide on real writing, not on how you'd like to sound. Collect:

• 3 to 5 pieces you're proud of. An email, a web page, a social post, a support reply. Mix formats if you can.
• 1 or 2 pieces that felt off-brand. Write a line on why: too stiff, too salesy, too long.
• A note on your readers. Who they are and what they care about. Use your clients' own words from emails, reviews or calls where possible.
• Your word habits. Words and phrases you always use, and ones you never use.

Optional shortcut: paste your good samples into an AI chat and ask it to describe the voice as a list of rules. Treat the answer as a first draft. It can spot patterns, but it can't know your audience or your red lines.

Step by step: build your brand voice guide

Each step below produces one section of the template further down. One principle runs through all of them.

Step 1: Describe your reader in two or three sentences

Cover who they are, what they already know, what they worry about and what they want from you. Add a line on jargon tolerance or reading level.

Too vague: 'Small businesses who need bookkeeping.'

Useful (Hollow Lane, fictional): 'Sole traders, tradespeople and small shop owners in our town. They're good at their trade but find bookkeeping stressful, and many are behind on their records and a bit embarrassed about it. They want someone to take the admin off their plate without judging them. Explain accounting terms the first time you use them.'

The second version tells the AI what to explain, what to reassure people about and what to avoid (judgement).

Step 2: Turn voice adjectives into rules

This is the core technique. Pick 3 or 4 traits. For each one, write what it means in practice and what it does not mean.

Step 3: Set tone shifts by context

Voice is your personality, and it stays the same everywhere. Tone is how that personality adjusts to the situation. The AI needs to be told when to adjust.

Step 4: Write your word list

Give the AI concrete vocabulary. Keep the list to roughly 10 to 20 entries so it stays readable. For Hollow Lane (fictional):

• Use: clients (not customers), your books (not financial records), monthly check-in (not consultation), tax return (not filing).
• Avoid: leverage, seamless, unlock, elevate, empower, solutions, hassle-free, game-changer, 'In today's…', 'take your business to the next level'.
• Spell exactly: Hollow Lane Bookkeeping (not HollowLane), Xero, QuickBooks.

Step 5: Add formatting and mechanics rules

AI tools are often inconsistent on house style. Spell it out:

• UK or US spelling, plus date and currency formats (for example '3 March 2026' and '£1,200').
• Paragraph length, when to use headings and bullets, and sentence case or title case for headings.
• Emoji policy and exclamation mark policy.
• Default length per format. Set these yourself, for example social posts under 60 words and emails under 150 words, unless the request says otherwise.

Step 6: Add good and bad examples

Examples are often the most effective part of the guide. Include 2 or 3 short pairs: an off-brand and an on-brand version of the same message, with a one-line note on why the bad one is wrong. The note helps the AI learn the principle rather than just copy the sentence.

• Bad: 'We're thrilled to offer seamless, cutting-edge bookkeeping solutions that unlock your business's full potential!'
• Good: 'We keep your books up to date each month, so you know where you stand and there are no surprises at tax time.'
• Why: banned words, vague claims and an exclamation mark. The good version says what we actually do.

Use real snippets from your own content where possible. Keep examples short so they don't eat the instruction space.

Step 7: Set hard limits on facts, claims and sensitive topics

This section protects your business from the AI inventing things in your name.

• Never invent prices, statistics, testimonials, guarantees, dates or client names.
• When information is missing, use a placeholder like [PRICE] or [DATE] and list what's needed, rather than guessing.
• Add industry-specific limits. For Hollow Lane: no tax or legal advice beyond general information; suggest a call for specific questions.
• State that a human reviews everything before it is published or sent. That's a reminder for your team as much as for the AI.

Copy-paste brand voice guide template

Fill in the bracketed parts and delete any lines you don't need. It's written as direct instructions to the AI.

BRAND VOICE GUIDE: [BUSINESS NAME] (version [1.0], [DATE], owner: [NAME])

ROLE AND PURPOSE
You write [TYPES OF CONTENT] for [BUSINESS NAME], [ONE-LINE DESCRIPTION OF THE BUSINESS]. Follow every rule below. If a request conflicts with these rules, follow the rules and say which one applied.

AUDIENCE
Write for [WHO THEY ARE]. They already know [WHAT THEY KNOW]. They worry about [MAIN WORRIES]. They want [WHAT THEY WANT FROM US].
[JARGON RULE, e.g. Explain any technical term the first time you use it.]

VOICE
Our voice is [TRAIT 1], [TRAIT 2], [TRAIT 3] and [TRAIT 4].
- [TRAIT 1] means: [RULES]. It does not mean: [WHAT TO AVOID].
- [TRAIT 2] means: [RULES]. It does not mean: [WHAT TO AVOID].
- [TRAIT 3] means: [RULES]. It does not mean: [WHAT TO AVOID].
- [TRAIT 4] means: [RULES]. It does not mean: [WHAT TO AVOID].

TONE BY CONTEXT
- Support replies: [TONE RULE]
- Social posts: [TONE RULE]
- Sales and service pages: [TONE RULE]
- Bad news: [TONE RULE]
If the context is not listed, use the support reply tone.

WORD LIST
Use: [TERM] (not [ALTERNATIVE]); [TERM] (not [ALTERNATIVE]).
Never use: [WORD], [WORD], [PHRASE], [PHRASE].
Spell exactly: [BRAND NAME], [PRODUCT NAMES].

FORMATTING
- Spelling: [UK/US] English. Dates: [FORMAT]. Currency: [FORMAT].
- Paragraphs: no more than [N] sentences. Headings in [sentence/title] case.
- Emoji: [POLICY]. Exclamation marks: [POLICY].
- Default length: social posts under [N] words, emails under [N] words, web sections under [N] words, unless the request says otherwise.

EXAMPLES (use for style only; do not reuse these phrases)
Bad: [OFF-BRAND VERSION]
Good: [ON-BRAND VERSION]
Why: [ONE LINE]
[Repeat for 2 to 3 pairs.]

HARD LIMITS
- Never invent prices, statistics, testimonials, guarantees, dates, client names or results.
- If a fact is missing, write a placeholder such as [PRICE] or [DATE] and list what you need at the end.
- [INDUSTRY RULE, e.g. Do not give legal, tax or medical advice beyond general information.]
- [OTHER LIMIT, e.g. Do not name competitors.]

WHEN UNSURE
If the request is unclear or missing key facts, ask up to [3] short questions before writing. If told to write anyway, use placeholders. A human will review everything before it is published or sent.

Filled-in example: Hollow Lane Bookkeeping (fictional, for illustration only)

BRAND VOICE GUIDE: Hollow Lane Bookkeeping (version 1.0, [DATE], owner: [NAME])

ROLE AND PURPOSE
You write emails, social posts, support replies and web copy for Hollow Lane Bookkeeping, a two-person bookkeeping firm for sole traders and small shops in [TOWN]. Follow every rule below. If a request conflicts with these rules, follow the rules and say which one applied.

AUDIENCE
Write for sole traders, tradespeople and small shop owners. They are good at their trade but find bookkeeping stressful. Many are behind on their records and feel embarrassed. They want the admin handled without being judged. Explain accounting terms the first time you use them.

VOICE
Our voice is friendly, confident, plain and calm.
- Friendly means: use 'you' and 'we', use contractions, keep most sentences under 20 words. It does not mean: slang, jokes, or exclamation marks in a row.
- Confident means: make direct recommendations and say what we do and don't do. It does not mean: hedging, or superlatives like 'best' or 'leading'.
- Plain means: one idea per sentence, short words. It does not mean: talking down to the reader.
- Calm means: acknowledge stress, then give the next step. It does not mean: urgency, alarm or false cheer.

TONE BY CONTEXT
- Support replies: calm and practical. If we got it wrong, apologise once, plainly, then fix it.
- Social posts: lighter and short. One useful point. No hard sell.
- Service pages: what's included and who it's for. No pressure or fake deadlines.
- Bad news: lead with the news, explain briefly, say what happens next.
If the context is not listed, use the support reply tone.

WORD LIST
Use: clients (not customers); your books (not financial records); monthly check-in (not consultation); tax return (not filing).
Never use: leverage, seamless, unlock, elevate, empower, solutions, hassle-free, game-changer, 'In today's...', 'take your business to the next level'.
Spell exactly: Hollow Lane Bookkeeping, Xero, QuickBooks.

FORMATTING
- Spelling: UK English. Dates: 3 March 2026. Currency: £1,200.
- Paragraphs: no more than 3 sentences. Headings in sentence case.
- Emoji: none, except at most one in social posts. Exclamation marks: at most one per piece.
- Default length: social posts under 60 words, emails under 150 words, web sections under 200 words, unless the request says otherwise.

EXAMPLES (use for style only; do not reuse these phrases)
Bad: We're thrilled to offer seamless, cutting-edge bookkeeping solutions that unlock your full potential!
Good: We keep your books up to date each month, so you know where you stand at tax time.
Why: banned words, vague claims, exclamation mark.

Bad: We sincerely apologise for any inconvenience this may have caused.
Good: You're right, we sent your figures late. That's on us, and they're attached now.
Why: stock phrase that doesn't admit anything.

Bad: Our prices start from just £50 a month!
Good: Our monthly package costs [PRICE]. (Ask for the price if it isn't given.)
Why: the price was invented.

HARD LIMITS
- Never invent prices, statistics, testimonials, guarantees, dates, client names or results.
- If a fact is missing, write a placeholder such as [PRICE] or [DATE] and list what you need at the end.
- Do not give tax or legal advice beyond general information. Suggest booking a call for specific questions.
- Do not name other firms.

WHEN UNSURE
If the request is unclear or missing key facts, ask up to 3 short questions before writing. If told to write anyway, use placeholders. A human will review everything before it is published or sent.

How long your guide should be

Aim for a guide that fits comfortably inside your tool's instruction space. Some tools cap custom instructions at a fixed number of characters, while projects and custom assistants often allow more. Limits vary by tool and plan and change over time, so check the vendor's help page before pasting.

Good vs bad AI output: examples using the guide

The table below shows the kind of difference a guide makes.

Notice that the on-brand versions don't repeat the example sentences from the guide. That's the goal: same style, fresh wording.

Subtler failures to watch for

These are easy to miss because the output looks on-brand at a glance:

• Right words, wrong length. A 'social post' that runs to 150 words.
• On-brand tone, invented facts. A friendly, calm email that quotes a price or turnaround time nobody gave it.
• Overcorrection. 'Friendly' becomes 'Hey there, money buddy!' That's why the 'does not mean' column exists.
• Copied examples. The same line from your examples, such as 'that's on us', turning up in every reply.

Where to put your guide in popular AI tools

Most tools have somewhere to store standing instructions, so you don't have to paste the guide every time. Use this table as a starting point and confirm the details on each vendor's help page.

If you haven't picked a tool yet, our guide to choosing an AI writing assistant for your business covers the criteria and tool types.

How to test your brand voice guide before your team uses it

Testing here doesn't mean judging whether the writing is 'good'. It means checking outputs against your own rules. That makes the result something you can share with your team and repeat after every change.

Build a 5-task test set

Pick 5 real tasks that cover different formats and tones. For Hollow Lane (fictional), the set might be:

1. Short social post: 'Write a social post reminding sole traders to send their receipts before the end of the month.'
2. Client email: 'Write a welcome email to a new client who has just signed up for our monthly package.'
3. Complaint reply: 'A client says we sent their quarterly figures two weeks late and they missed a meeting with their bank. Write a reply.'
4. Longer web section: 'Write the intro section for our monthly bookkeeping service page.'
5. Tricky task with missing information: 'Write an email telling clients our prices are going up.' (No new price, date or reason given. A good result asks questions or uses placeholders. A bad one invents numbers.)

Run the test

The same test set can double as part of a tool trial. See our 5-day trial plan for AI writing tools.

Score outputs with a simple rubric

Score each output from 0 to 2 on each criterion: 0 = fails, 1 = partly meets the rule, 2 = fully meets it.

The maximum is 14 per task. Set your own pass threshold. For example: at least 12 on every task, and any 0 on 'no invented facts' is an automatic fail.

If possible, ask a second person to score the outputs without knowing which version of the guide produced them. It removes some of your own bias.

Fix one thing at a time and retest

Match what you see to a fix:

Keeping your guide working over time

• Expect drift. Outputs can slide away from the guide in long conversations. Start a new chat for each new task, or ask the AI to re-read the guide before an important piece.
• Retest regularly. Rerun the 5-task test when your tool updates its model. Many teams also make it a habit every few months, since tools can change without much notice.
• One master version. Store the guide in a shared document with a named owner. Copy that version into each tool rather than editing it in several places.
• Collect failures. Ask the team to save off-brand outputs. The clearest ones become new bad examples.
• Update when things change. A new service, a new audience, or the team fixing the same issue over and over are all signs it's time for a new version.
• Keep human review mandatory. Anything published or sent to clients gets read by a person first. Our AI acceptable use policy template can make that rule official for your whole team.

Common mistakes to avoid

• Only adjectives, no rules. 'Warm and professional' gives the AI nothing to check against.
• A guide so long it contradicts itself. Cut anything that isn't a rule, an example or a limit.
• No bad examples. Good examples alone don't show where the line is.
• No hard limits on facts. On-brand copy with an invented price is still a problem.
• Testing on one easy prompt. Use all five tasks, including the awkward one.
• Different versions in different tools. Keep one master copy.
• Expecting the guide to replace editing. It reduces rewriting. It doesn't remove review.

Quick checklist

• Audience defined in 2 to 3 sentences, with a jargon rule
• 3 to 4 voice traits turned into 'this means / does not mean' rules
• Tone set for support, social, sales and bad news
• Word list of about 10 to 20 entries
• Formatting rules, including default lengths
• 2 to 3 good and bad example pairs with a reason for each
• Hard limits on facts, claims and sensitive topics
• Guide pasted in the right place in your tool
• 5-task test passed at your chosen threshold
• Owner, version number and next review date set

Frequently asked questions

How long should a brand voice guide for AI be?

Aim for roughly one page of core rules plus a few short examples. That is usually short enough to fit the tool's instruction space and for the AI to apply consistently. Limits vary by tool and plan, so check the vendor's page. If it's too long, cut anything that isn't a checkable rule, an example or a hard limit.

Can I ask ChatGPT or Claude to write my brand voice guide for me?

Yes, as a first draft. Give it 3 to 5 samples of your best writing and ask it to describe the voice as a list of rules. Then edit hard: add your own word list, hard limits on facts and your bad examples, and test it on real tasks. The AI can't know your audience or your red lines.

What is the difference between brand voice and tone?

Voice is your consistent personality across everything you write. Tone is how that voice adjusts to the situation, for example a calm, apologetic complaint reply versus a lighter social post. A good guide states both, so the AI knows what stays fixed and what changes.

Will the AI follow my brand voice guide every time?

Not perfectly. Outputs can drift, especially in long chats or unusual tasks. Start a fresh chat for new tasks, restate the key rules for important pieces, and always have a person review anything before it is published or sent.

Where should I paste my brand voice guide?

Wherever the tool keeps standing instructions: custom instructions, Projects or custom GPTs in ChatGPT, Projects in Claude, Gems in Gemini, or brand voice and style guide features in dedicated writing tools. Pasting it at the start of a new chat works in any tool. Availability depends on the plan and changes over time, so check the vendor's page.

Should I include examples of competitors' writing?

Only as short 'not like this' references, if at all. Your own on-brand and off-brand examples are far more useful. Don't paste large chunks of other people's content into your guide.

Can one guide work across different AI tools?

Yes. Keep one master document and paste the same version into each tool. Then run the same 5-task test in each one, because different tools may interpret the same instructions differently.

How often should I update the guide?

Update it when your services or audience change, when the team keeps fixing the same issue, or after your tool changes its model. Rerun your 5-task test each time, and give the new version a number and date.