Input for guiding image asset generation with a freeform prompt.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v25/services/asset_generation_service.proto)

| Fields ||
|---|---|
| ## `freeform_prompt` | `string` Required. A freeform text description to guide the image generation process. The maximum length is 1500 characters. Required. |