Why an AI should quote prices only from a catalogue: the four ways prices go wrong in a chat, and the four rules that stop them

How prices go wrong

• A document says something the price list no longer does. The brochure PDF from March says ₹998; the plan is ₹999 now. The AI answers from the document, because that is where it looked.
• The customer says a number and the AI agrees. "So it's ₹500?" — "Yes." Now there is a quote in writing.
• The AI reasons its way to a price. Two items at ₹1,200 with 10% off: the model does the sum, gets it right most of the time, and the exception is a promise.
• The AI is asked and does not know, so it says "custom". A product with a listed price described as priced on request — a customer who would have bought, sent to a form.

Each of these happened, in a real product or a real conversation, and each is why the catalogue has to be the only place a price comes from.

The four rules

1. One authority. Products, variants, prices, in one catalogue the business edits. Documents may describe a product; they may not price it.
2. Attach the catalogue to every answer that touches a product. In code, not by asking the model to look: if the question or a passage names a product, the product's record — with its price — is put in front of the model first. A document that disagrees is out of date and the instruction says so.
3. Verify the reply. A price in the reply that the turn did not retrieve from the catalogue is refused before it sends. The model cannot state a number it did not look up.
4. Price the money things from the catalogue, never from the chat. A deal's value is the catalogue price of the products the customer showed interest in. A payment request is catalogue price times quantity; an amount the model writes into the request is ignored.

Discounts, negotiation, custom quotes

A discount is a rule a person wrote — "10% for orders above ₹10,000" — and the AI may apply it because the rule, not the model, holds the number. A negotiation is a handover: the customer who asks for a better price gets a person, with the fields filled. A custom quote — freight rates, a bespoke itinerary — is typed by a person into the record and sent as a template, and the deal opens at that number because a person decided it. A rep may always type a custom amount into a payment request; the AI may not.

What the customer experiences

A straight answer. "The Linen Kurta Set is ₹2,499, in stock in M and L, delivered to Pune by Thursday" — with the picture — in the first minute. Not "pricing varies", not a form, not a number that a person has to walk back tomorrow. That is most of what a customer wanted from the conversation, and it is only possible when the number is one nobody has to check.