ALL_REQUIRED

OpenAI Strict Mode (Default): All parameters are marked as required.

In strict mode, all parameters must be present in the required array. Optional/nullable parameters are represented using union types with null: ["string", "null"].

Example:

fun writeLog(level: String, exception: String? = null)

Generates:

{
  "required": ["level", "exception"],
  "properties": {
    "level": { "type": "string" },
    "exception": { "type": ["string", "null"] }
  }
}

This ensures the model always provides all fields, even if they're null.