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An AI writer hands back your product facts and then a few you never gave it. I ran one made-up product through the same writer five times, and every draft added something: a benefit, a performance promise, once a care instruction I never wrote. That is a complaint or a return waiting to happen, so the procedure ends with a check.
Every claim you will stand behind, in plain lines, nothing else. Mine, for an invented ceramic dripper, had 11:
Tidewell ceramic pour-over coffee dripper. Stoneware, hand-glazed, so the glaze colour varies slightly from piece to piece. Colours: Sand, Slate, Moss. Fits standard #2 cone paper filters (filters not included). Single drain hole. Brews 1 to 4 cups. 11.5 cm tall, 380 g. Top-rack dishwasher safe. Made in Portugal. Price $34.
Fed only the name and price, the writer wrapped 5 invented phrases around those two facts in 62 words, one a claim about "optimal water temperature and flow" I cannot test. Fed all 11 facts, it returned all 11. The sheet is also what you check against later.
The writer is one tile in the grid on rewind.ai's free ai no login page, next to chat, image and voice tools. It asks you to sign up after, not before. Content type Product Description, Length Short, fact sheet in as the topic.
The Additional Instructions box is real: the page sends all four settings to the model as plain text lines in one prompt, so what you type arrives word for word. By the site's own accounting my five cost 8 to 17 each, median 12, from a 2,500-token daily pool with no account. A run needs 150 free in a pool shared behind your connection; one of mine hit an empty pool and got an error. Short is a hint: my drafts ran 44 to 126 words.
Professional or Friendly. Same brief, no instructions: my Persuasive run produced 10 invented phrases to the Professional run's 5 and lost the drain hole too. One run each, so I will not say it always does that; I just do not pick it for a spec-heavy product.
My first guard said facts only, "Under 120 words", "End with a 4-item bullet list of specs". The model met the caps by dropping facts: 5 of 11 survived, with one invented phrase, and the glaze note, cups, size and weight, the dishwasher line, country and price all gone. Never cap the list below your fact count.
The version I paste now:
Use every fact provided and only those facts. Do not add any feature, material claim, certification, benefit or number that is not listed. Keep care instructions word for word. End with a bullet list of all specs.
That run kept 10 of 11 facts and "top-rack" twice, where both unguarded full-brief runs had flattened it to "Dishwasher safe". Only the price went missing; the store page shows it anyway.
This is the step. Draft beside sheet, line by line. Anything the sheet does not say goes; any qualifier that went quiet comes back.
No setting removed this step. The strictest still wrote the care line. None is safe; the last is the best of the five.
Same product, Short throughout:
| Brief | Tone | Additional instructions | Facts kept of 11 | Invented phrases | Tokens |
|---|---|---|---|---|---|
| name and price | Professional | none | n/a, two given | 5 | 8 |
| full | Professional | none | 11, "top-rack" dropped | 5 | 12 |
| full | Persuasive | none | 10, drain hole and "top-rack" dropped | 10 | 13 |
| full | Friendly | first guard, capped | 5 | 1 | 8 |
| full | Friendly | second guard, no cap | 10, price omitted, "top-rack" kept | 5, one a care line | 17 |
Before and after, verbatim. The thin brief, Professional, no instructions:
Introducing Tidewell Ceramic Pour-Over Coffee Dripper. Crafted from premium ceramic, the Tidewell Pour-Over Coffee Dripper offers an unparalleled brewing experience. Its sleek, minimalist design complements any kitchen aesthetic while ensuring optimal water temperature and flow for a perfectly extracted cup of coffee. At $34, this pour-over dripper is a thoughtful investment for coffee enthusiasts seeking quality and elegance in their daily routine.
Strike: "premium ceramic", "an unparalleled brewing experience", "sleek, minimalist design complements any kitchen aesthetic", "ensuring optimal water temperature and flow for a perfectly extracted cup of coffee", "a thoughtful investment for coffee enthusiasts".
The full brief, Friendly, second guard, with the accurate lines cut and marked [...]:
Introducing Tidewell, your new favorite pour-over coffee dripper. [...] Fits standard #2 cone paper filters (filters not included). With a single drain hole, it brews 1 to 4 cups of perfectly balanced coffee. Standing at 11.5 cm tall and weighing 380 g, it adds both function and form to your kitchen. Top-rack dishwasher safe for easy cleaning. [...] a beautiful addition to any coffee enthusiast's collection. Care instructions: Handwash recommended, but top-rack dishwasher safe. [...]
Strike: "perfectly balanced coffee", "adds both function and form to your kitchen", the favorite line, the collection line, the whole care line. Keep "Top-rack". Best of the five, still 5 cuts.
Numerous is the better tool if your catalog lives in a spreadsheet. It runs as an add-on inside Google Sheets or Microsoft Excel and its page says "Generate descriptions for multiple products at once." Filling a column beats pasting one product at a time into a web form; Numerous does that, the writer above does not. Account required, paid after a 7-day trial.
Grammarly's product description generator is the other free, no-account route, from a name you already know: details then tone, no length control stated, no free allowance published. Its own examples do what mine did: a headset prompt with a 40-hour battery came back with "Designed for comfort and all-day wear" and "seamless Bluetooth connectivity" added. No mark against Grammarly; these models do it, mine included, so the check stays whichever tool you pick.
On Shopify, Sidekick is included with your plan and writes into the admin itself, which nothing here matches.
Product Description, Short, a plain tone, and this in Additional Instructions, unchanged:
Use every fact provided and only those facts. Do not add any feature, material claim, certification, benefit or number that is not listed. Keep care instructions word for word. End with a bullet list of all specs.
Then the sheet in one window, the draft in the other, and every sentence either matches a line or goes. Last thing before anything reaches the store.
Language models fill gaps with plausible marketing phrases, especially when the brief is thin. The fewer facts you provide, the more the model invents, which is why a complete fact sheet matters.
Clear instructions reduce invented claims but do not remove them. In these tests even the strictest guard still produced an invented care line, so a manual check is always needed.
Be careful with tight limits. A word or bullet cap can push the model to drop real facts to fit, so any limit should leave room for every fact on your sheet.
A plain tone such as Professional or Friendly tends to stay closer to the facts. Persuasive settings produced more invented phrases and dropped product details in testing.
Compare each sentence with your fact sheet. Remove anything the sheet does not support, restore qualifiers that were dropped, and make sure care instructions match word for word.
