How do you find out what the customer means?
Start with the product and the decision. A photo, a short name or “the blue one” may not identify a unique item. Ask for a product link or variant when needed. Do not assume the most recently promoted item is the one they mean.
Fictional example: A customer asks whether a bag fits a laptop. A useful reply is: “Which laptop dimensions should we check, and which bag are you considering?”
The answer can then compare the published compartment dimensions. It should not guarantee fit from screen size alone when the casing or shape may differ. Explain the missing information in ordinary language so the customer understands why you asked.