Structured Output Constraint via Enum

const schema = {
  type: "object",
  properties: {
    sentiment: {
      type: "string",
      enum: "positive, negative, neutral"
    }
  },
  required: ["sentiment"]
};

await client.responses.create({
  model: "gpt-4o-mini",
  input: "Classify: 'I love this!'",
  response_format: { type: "json_schema", json_schema: { name: "s", schema } }
});