OpenAI Decisions API vs Responses API

What each API is for

The Responses API is the general workhorse: send text or images, get back generated text, schema-constrained JSON, or tool calls, and keep a conversation going across turns. It is the endpoint you use when the model has to produce something new.

The Decisions API is narrower by design. You send context plus a question with a finite set of answers you define, and it returns one of those answers — with a probability per option and a confidence, per OpenAI's announcement. It is in limited preview as of 2026-09-30, with broad release announced for the coming days. The endpoint on this site runs the same finite-answer pattern today on decisions-1.

Side by side

A decision on the Responses API today

You can already approximate a decision with the Responses API: constrain the output with a JSON schema and an enum. You get back a valid label — but no per-option probabilities for the runner-ups.

// OpenAI Responses API: ask for a label inside a JSON schema.
// You get a label — not a probability per option.
const res = await client.responses.create({
  model: "YOUR_MODEL",
  input: "The page renders blank in Safari. Route this ticket.",
  text: {
    format: {
      type: "json_schema",
      name: "route",
      strict: true,
      schema: {
        type: "object",
        properties: {
          team: { type: "string", enum: ["payments", "frontend", "account"] },
        },
        required: ["team"],
        additionalProperties: false,
      },
    },
  },
});
// res.output_text -> { "team": "frontend" }

The same task as a decision request

As a choice question on this site's endpoint, the same routing task returns the winning label, a probability for every option, and a confidence — the inputs you need to auto-route the clear cases and escalate the close ones.

// decisions-1 on this site: the same routing task as a choice question.
const res = await fetch("https://decisions-api.net/api/v1/decisions", {
  method: "POST",
  headers: {
    Authorization: "Bearer YOUR_KEY",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    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.",
        },
      },
    },
  }),
});
// Illustrative response: answers.team ->
//   { choice: "frontend", probabilities: {...}, confidence: 0.86 }

When to use which

Use the Responses API when the model has to produce content: draft the reply, write the summary, call the tool. Use a decision API when the model has to choose — which queue, which branch, which next action — and when you need the distribution to decide whether to trust it.

They compose well: a decision call picks the branch, then a Responses API call writes the reply for that branch. Choosing and writing are different jobs.

FAQ