The Merchant API is in closed beta, and the behavior might change at any time. If you plan to use the Merchant API for your implementation, be prepared to make updates with short notice. Ask your Google representative for frequent updates.
During the Merchant API closed beta, we might make breaking changes without updating the major version. We'll give at least 12 days of notice before making a breaking change. For the duration of the closed beta, all sub-APIs will remain on v1beta.
The discovery URL for the Merchant API isn't available during the closed beta.