OpenAI's documentation distinguishes "Structured Outputs" from the older "JSON mode" feature of its Chat Completions / Responses APIs. According to that documentation, what is the key difference between the two?
- Both guarantee syntactically valid JSON, but only Structured Outputs also guarantees the output conforms to the caller's supplied JSON Schema (for example, required keys and enum values); JSON mode guarantees valid JSON syntax only
- JSON mode guarantees schema conformance, while Structured Outputs only guarantees syntactically valid JSON without any schema checking
- Structured Outputs can only be used with image inputs, while JSON mode is restricted to text-only prompts
- The two features are functionally identical; "Structured Outputs" is simply a rebranding of "JSON mode" with no change in behavior
Correct answer: A. Both guarantee syntactically valid JSON, but only Structured Outputs also guarantees the output conforms to the caller's supplied JSON Schema (for example, required keys and enum values); JSON mode guarantees valid JSON syntax only
OpenAI's documentation states that Structured Outputs "ensures the model will always generate responses that adhere to your supplied JSON Schema," explicitly calling it "the evolution of JSON mode," while JSON mode only ensures the output parses as valid JSON without enforcing that it matches any particular schema, meaning JSON mode output can still omit required fields or use invalid enum values even though it is syntactically valid JSON. The second option reverses the actual guarantees documented by OpenAI. The third option is wrong because the distinction has nothing to do with input modality; both features concern the format of the model's text output regardless of whether the request includes image inputs. The fourth option is wrong because the documentation explicitly frames Structured Outputs as adding a stricter guarantee, schema adherence, that JSON mode does not provide, rather than describing an identical rebrand.
Source: OpenAI, "Structured Outputs" documentation, platform.openai.com/docs/guides/structured-outputs