Vaulted Tokenization uses HTTP Basic Authentication. API credentials can be obtained on the API page (found under Settings > Preferences > API) of ALTR's portal for Enterprise + customers. Usernames are the 'Key Names' listed on that page, and Passwords are the 'Key Secret' provided when an API key is created.
Up to 4096 values can be detokenized at once. Using smaller batch sizes may improve performance.