Structured output format

{
  "type": "json_schema",
  "json_schema": {
    "name": "your_schema_name",
    "strict": true,
    "schema": {
      "type": "object",
      "properties": {
        "property1": { "type": "string" },
        "property2": { "type": "number" }
      },
      "required": ["property1", "property2"],
      "additionalProperties": false
    }
  }
}

{
  "type": "json_schema",
  "json_schema": {
    "name": "city_info",
    "strict": true,
    "schema": {
      "type": "object",
      "properties": {
        "country": { "type": "string" },
        "state": { "type": ["string", "null"] },
        "city": { "type": "string" },
        "zipcode": { "type": "string" }
      },
      "required": ["country", "state", "city", "zipcode"],
      "additionalProperties": false
    }
  }
}