Represents a callout extension.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/common/extensions.proto)

| Fields ||
|---|---|
| ## `callout_text` | `string` The callout text. The length of this string should be between 1 and 25, inclusive. |