OpenAI Decisions API vs Structured Outputs

The actual difference

Structured Outputs constrain the shape of the response — the model must produce JSON matching your schema. If you ask it for a label inside that schema, you get a label, and nothing about the runner-ups.

A decision call constrains the semantics — the model picks one of your finite answers and returns a probability for every option plus a confidence value. The second-place option and its probability are the whole point: they tell you whether to act automatically or escalate to a human.

Side by side

Structured Outputs give you a parseable enum field. The decision endpoint gives you the same enum plus the distribution behind it.

// Structured Outputs: the model fills a JSON schema.
// You get a parseable label — not a probability per option.
{
  "response_format": {
    "type": "json_schema",
    "json_schema": {
      "name": "route",
      "schema": {
        "type": "object",
        "properties": {
          "team": { "enum": ["payments", "frontend", "account"] }
        }
      }
    }
  }
}

The decision version

Same routing task, expressed as a choice question. The response carries the winner, the per-option probabilities, and a confidence — enough to auto-route at 0.8 and escalate below it.

// Decision endpoint: the answer carries a probability
// for every option plus a confidence — enough to set a threshold.
{
  "model": "decisions-1",
  "state": "The page renders blank in Safari.",
  "questions": {
    "team": {
      "type": "choice",
      "instructions": "Which team should own this ticket?",
      "criteria": {
        "payments": "Checkout or billing.",
        "frontend": "Rendering or browser behavior.",
        "account": "Login or permissions."
      }
    }
  }
}

When to use which

Use Structured Outputs when you need the model to produce data — extraction, form filling, multi-field responses where every field matters. Use a decision endpoint when the model's job is to pick one branch and you need to know how close the call was.

They compose cleanly: a decision call picks the route, then a structured generation produces the payload for that route.

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