Hallucination
A hallucination is a fluent, confident statement by a language model that is false or unsupported: an invented fact, price, policy or appointment slot presented as if it were known.
Also called: confabulation, fabrication
Language models generate likely-sounding text. When they lack the information to answer, they may produce an answer anyway, and it will sound exactly as assured as a correct one. For a receptionist that means quoting an opening time it was never given, confirming a booking it did not make, or describing a service the business does not offer.
Hallucination is not random; it is most likely when the model is asked something outside what it has been provided, or when instructions are vague. The remedies are structural: grounding the agent in the business’s actual information, letting it look things up rather than recall them, instructing it to say when it does not know, and guardrails that keep it off topics it has no facts for.
When evaluating a voice agent, ask it something the business has not told it and listen for whether it admits the gap or fills it.