Article
Zero-Hallucination Choices: How the Decisions API Guarantees Its Output
A model that cannot write outside a declared set cannot hallucinate a choice that was never offered. That is the Decisions API guarantee, and it simplifies production reasoning.
What the guarantee is
The Decisions API response is mathematically bound to the choices you provide. Given choices ['refund', 'request_info', 'escalate'], the API returns one of those three — never a fourth label, never free text, never an empty answer. There is no parsing layer to make a mistake.
What it means in production
The guarantee moves a class of bugs out of the system:
- No invalid enum values reaching downstream services
- No retry-and-repair logic around the decision call
- No fallback mapping for unexpected model output
The boundary to remember
The model still decides which choice is right for the context. The guarantee is about form, not about judgment — which is exactly the right trade: the system controls the options, the model does the classification.