A developer adds the instruction 'Always return a JSON object with keys: action, confidence, and reason' to their system prompt. The model occasionally omits the confidence field. What is the most reliable fix?
Answer: Use response_format with a JSON schema that marks confidence as required
JSON schema enforcement via response_format is a programmatic control at the API layer — the API rejects responses that don't include the required confidence field before they reach your code. Prompt instructions (A, B) are prompt-based controls that the model can occasionally drift from, especially on edge cases. Post-processing (D) masks the root cause and requires writing logic to determine what the default confidence should be — which may produce incorrect data.