This article shares a possible use case for your app. You're certainly not limited to this use case, but it might be a helpful start to plan your app's implementation.
The owners of a fitness blog would like to increase revenue by displaying advertisements on their Wix site. Your app will modify the existing Ads.txt file to enable a content discovery platform as an authorized seller.
To add an authorized digital seller, your app will call the Append Ads.txt endpoint. You’ll need to pass the platform’s name, account id, payment type, and tag id inside the content field of the adsTxt object. You can read more about the structure of Ads.txt files on the IAB’s website.
Notice that the content field in the response has two lines, separated by the new line (\n) control character.