Code as Business Rules Constraint

The principle of “constraints over guidance”: a rule enforced in code means “must not do”, while in a prompt it only means “recommended not to do”. The τ-bench (triple-guarantee) pattern: rules in natural language in the system prompt (for understanding and explanation); a tool description with expected_* parameters acts as a thinking checklist for the model; server-side codified validation against ground truth DB data is the final gatekeeper. Key detail: no policy fact is taken from parameters claimed by the model – the model can hallucinate or be manipulated by prompt injection.

Related: [Code as a Meta-Capability], [Harness Engineering], [Prompt Injection]