There are currently two Buyer REST API versions: Version 1, and the new version 2 that is currently in open beta.
Version 1 of the Buyer REST API allows you to:
- Access real-time bidding account information
- Submit creatives for verification
- Check the status of a submitted creative
- Retrieve performance reports
- Retrieve pretargeting configurations
Version 2 will eventually replace version 1. It's currently used to configure Client Access for Marketplace.