How to use AI to write product descriptions for your online store in your brand voice

You copy a product description out of ChatGPT, paste it into your store, and something's just... off. It's technically correct. It covers the features. But it sounds like it was written by a very polite robot who has never actually held your product. And somehow your customers can tell.

This post shows you how to get AI product descriptions that sound like your brand voice — not like every other store on the internet.

The trick isn't a fancier tool. It's a five-minute setup step most people skip entirely.

What you need before you start

ChatGPT — a text-based AI that writes copy when you describe what you need; the free version works, but GPT-4o (the paid tier at around $20/month) gives noticeably better results for creative copy.

Shopify Magic — Shopify's built-in AI writing tool, included free with any Shopify plan, available directly inside your product editor.

Canva Magic Write — Canva's AI writing feature, built into Canva's design editor; useful if you're creating product images and descriptions together.

Time required: About 30–45 minutes to set everything up the first time. After that, each new product description takes roughly 5 minutes.

Skill level: If you can write an email and copy-paste text, you're fully qualified to do this.

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Build Your Brand Bible First (It Takes 15 Minutes and Saves You Everything)

Here's why generic AI copy fails: AI tools don't know your voice unless you show them. They're not guessing badly on purpose — they just default to "average internet English," which is nobody's brand.

The fix is something called a Brand Bible. Think of it like a cheat sheet you hand to a new employee on their first day. Except the employee is a very fast writer with no personality of their own.

1. Open a blank document — Google Docs, Notes, anywhere works.

2. Write your "preferred words" list. These are words or phrases you actually use in your store, your emails, or when you talk about your products. If you sell handmade candles and you always say "hand-poured" instead of "handcrafted," write that down. If you run a gym and say "earn it" instead of "achieve your goals," put that in. Aim for 10–15 phrases.

3. Write your "banned words" list. These are the flat, corporate words AI loves and you hate. Common offenders: elevate, unlock, seamlessly, robust, transform, game-changer. Add anything that makes you wince when you read it. Keep this list growing.

4. Paste in 3–5 of your best existing product descriptions. If you don't have 5 great ones, use 2–3 and your best email or social post. The AI will pattern-match from these better than any instruction you can write.

5. Add two or three sentences about who your customer is. Not demographic data — more like: "She's a 35-year-old who shops on her lunch break and wants to feel like she's buying something special, not just useful."

That's your Brand Bible. One document. Keep it somewhere you can grab it fast.

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Set Up ChatGPT Custom Instructions for Brand Voice Consistency

Every time you start a new chat in ChatGPT, it forgets everything about you. It's like calling a contractor who has zero memory of your house, every single time. Custom Instructions fix that.

1. Log into ChatGPT and click your name or profile icon in the bottom-left corner.

2. Select "Custom Instructions" from the menu. This is a system-level setting — it runs quietly in the background of every conversation you have.

3. In the first box ("What would you like ChatGPT to know about you?"), paste a condensed version of your Brand Bible: your preferred words, your banned words, your customer description, and one or two example descriptions.

4. In the second box ("How would you like ChatGPT to respond?"), add your formatting preferences.

This prompt works well for that second box — it tells the AI exactly how to behave rather than just what to know:

Write product descriptions in the voice shown in my examples. Use my preferred words list. Never use words from my banned list. Keep descriptions between 80–120 words unless I ask for something longer. Always lead with the benefit, not the feature. Match the warmth and specificity of my example copy.

5. Click Save. Now every new chat session starts with your brand context already loaded.

Once this is set up, writing a new product description is genuinely fast. You paste in the product specs — material, size, what it does — and ChatGPT writes a first draft that already sounds closer to you than anything it generated before.

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Using Shopify Magic and Canva Magic Write (and Where Each One Fits)

These tools are convenient, but they work differently from ChatGPT. Worth knowing the difference before you commit to one.

Shopify Magic lives inside your Shopify product editor. You click "Write with AI," pick a tone (playful, sophisticated, daring), and it generates a description. Fast and useful for one-off products — but the tone options are broad categories, not your specific voice.

The workaround: after generating, go into Shopify's backend and manually update the product metadata fields with your brand-specific adjectives. Think of the AI-generated text as a rough frame — you're adding the paint. Takes an extra two minutes but makes a real difference in how the final copy reads.

Canva Magic Write is great if you're already in Canva designing product images. It writes descriptions right inside the template, so your copy and visuals develop together. The catch is that it doesn't have long-term memory like ChatGPT's Custom Instructions. Every time you open a new design, you're starting fresh.

Best use for Canva Magic Write: one-off product launches, seasonal items, or anything where you're building the visual and the copy at the same time. For bulk catalog updates, go back to ChatGPT.

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A Note for Etsy Sellers

If you sell on Etsy, you may have noticed the platform has its own AI assist tool. It's optimized for SEO (helping your listing show up in search) and character limits rather than creative voice. It's good at structure. It's not great at personality.

The workflow that works best: write your description in ChatGPT with all your Brand Bible context loaded, then paste the finished copy into Etsy. You keep the voice, and you can then adjust keywords manually to hit what Etsy's search engine rewards. Best of both worlds.

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The 80/20 Rule: Why You Still Need to Touch Every Description

Here's something worth saying plainly. AI is genuinely good at the structural 80% of a product description — dimensions, materials, care instructions, what it does, who it's for. That part? Let the AI handle it.

The remaining 20% is yours. It's the emotional hook — the line that makes someone feel something. "Made for the mornings when you actually have ten minutes to yourself." "Tough enough for a job site, light enough to forget it's there." That kind of line doesn't come from a prompt. It comes from knowing your customer the way only you do.

Read every AI draft out loud before you publish it. If you stumble on a sentence, rewrite it. If it sounds like a brochure for a company you'd never buy from, cut it. Your goal isn't to remove the AI's work — it's to finish it.

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What to do next

Start with just one product. Take your best-selling item, build your Brand Bible from what you already know about it, set up ChatGPT Custom Instructions, and write one description using the full process above. Compare it to what you had before.

If you want to go further with automating your store's marketing copy, [we've got a walkthrough on building a simple AI content workflow for product launches](PENDING: AI content workflow for small business product launches).

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FAQ

Does this work if I've never written a "brand voice" document before?

Completely. Most small business owners haven't — it's one of those things that sounds formal but doesn't need to be. Your Brand Bible can literally be a list of words you like and a few sentences about your customer. If you've ever described your business to a friend, you already know what goes in it.

Can I use the free version of ChatGPT for this?

Yes, the free version supports Custom Instructions and will write decent product copy. The paid GPT-4o model handles nuance better — longer examples, more subtle voice — but free is a perfectly good place to start.

How do I handle SEO if I'm writing for voice first?

Write for voice first, then check your keywords. Once you have a description you like, read through it and see where a keyword fits naturally. If it doesn't fit naturally, add it to the metadata or title field instead. Stuffing keywords into copy that's otherwise well-written tends to hurt more than it helps.

What if the AI keeps ignoring my banned words list?

This happens. AI tools sometimes drift, especially in longer sessions. The fix is to add your banned words list directly into the product description prompt itself, not just the Custom Instructions. Something like "Do not use: elevate, unlock, seamlessly, robust" right in the prompt gives it a second reminder in context.

Is Shopify Magic worth using if I already have ChatGPT set up?

They're good for different moments. Shopify Magic is faster for quick edits when you're already inside the platform managing inventory. ChatGPT with Custom Instructions gives you more control over voice and is better for new products or bulk writing sessions. A lot of store owners use both — Shopify Magic for speed, ChatGPT for anything that needs to be really on-brand.