Message Bus is a cloud-native application service for email and mobile messaging. The selling point is the high deliverability rate, its ability to scale according to demand and the fact that it's simple enough to be used by developers with limited time and resources. The Message Bus API makes it possible for developers to easily add messaging functionality to their websites and apps.
The Streak API integrates its client relationship management (CRM) platform into other applications like MailChimps and Wufoo. The API's webpage reveals that it requires an API key and uses HTTP Basic Auth. The request format supports Create, retrieve, update, and delete (CRUD) with response in JSON. The purpose of the API is to manage CRM relationships through your application.