Did your AI change a price or a date?
How to check an AI rewrite before you send it, by hand or automatically.
Why rewrites change facts
Chat AI writes by predicting likely words. That makes it good at tone and flow, but it has no rule that says “keep NZ$1,250 exactly as it was”. While it smooths a sentence it may round a number, swap a date format, drop a condition or turn a firm promise into a soft one. The new version reads well, which is why the change is easy to miss.
What tends to go wrong
| Your original | The AI rewrite | What changed |
|---|---|---|
| NZ$1,250 + GST | about NZ$1,200 | Price and GST |
| Due Friday 14 November | Due mid-November | Date |
| Deposits are not refundable | Deposits are refundable on request | A negation |
| We will deliver by 9 am | We aim to deliver in the morning | A softened promise |
| Only if paid within 7 days | Paid within 7 days | A dropped condition |
| Whangārei | Whangarei | A missing macron |
These examples are made up to show the kinds of change, but each kind is common. One of them in a quote or a policy can cost money or trust.
A checklist to use by hand
- Numbers. Every price, quantity, percentage and unit matches the original, including GST wording.
- Dates and times. Same day, date, time and how often (“weekly” is not “monthly”).
- Names and links. People, businesses, places and web addresses are spelt as they were, macrons included.
- Small words. “Not”, “only”, “unless”, “must” and “will” are still there.
- Lists and quotes. No item dropped, and quoted words are still word for word.
- Placeholders. No leftover [name] or [date] in the text you are about to send.
Reading side by side works for one email. It doesn’t work for fifty product descriptions or a long policy, and it’s exactly the kind of checking people skip when they’re busy.
Checking rewrites automatically with Gnomon
Gnomon, from NOVA, compares your original with the AI’s version and flags prices, dates, times, numbers, units, names, links, negations, softened promises, comparisons, conditions, lists, quotes, placeholders, macrons, days and frequency. It ranks what it finds by risk, writes a fix-up message you can hand back to the AI, and its repair puts the original facts back into the rewrite.
- Fast and repeatable. A text check takes about 10 ms per 2,000 characters and uses no AI model, so the same texts give the same result every time.
- Private. Texts are never stored.
- Works with your AI. Add Gnomon to Claude or ChatGPT as a connector, or call the API from your own app. See how to add it.
- Priced in NZ dollars. Test keys are free for 100 checks a day. Live keys use prepaid credit at NZ$0.03 per 1,000 units, where a unit is 1,000 characters across both texts.
Gnomon can also check an AI answer against its sources and flag facts the sources don’t back up. For why AI gets things wrong in the first place, read How often is AI wrong?
Questions
Can AI change the facts when it rewrites my text?
Yes. Chat AI predicts likely wording, so while improving tone it can round a number, change a date, drop a condition or remove a word like “not”. Always compare a rewrite with the original before sending it.
How do I check an AI rewrite quickly?
Compare numbers, dates, names, links and small words such as “not” and “only” against your original. For many texts, a checker such as Gnomon does the comparison automatically.
Does Gnomon use AI to check AI?
Not for text checks. Gnomon’s text check uses no AI model, so it gives the same result every time and takes about 10 ms per 2,000 characters.
Does Gnomon keep my text?
No. Texts sent to Gnomon are never stored.
Check every rewrite before it goes out.
Free test keys give you 100 checks a day. Credit is in NZ dollars when you need more.