Most of the apps built using Voximplant have some client application that uses our Web or Mobile SDK, or other types of the endpoint communicating with Voximplant (like SIP client), but there are a couple of scenarios when there is no client application involved. The most common one is callback scenario when platform makes calls to the different destinations and join these calls while required. Or another one – automated notifications or surveys, when you want to call your customer and playback some important message or get the feedback. A special part of HTTP API available for Voximplant developers that makes these scenarios possible and easy to implement is called Control API (since it’s created for controlling sessions, unlike Provisioning API created to let you add/edit/delete different Voximplant entities, like app Users, Rules, etc.). Description of the API is available here, “How To” is available here. Learn more in our blog post about Control API.