The Voice2Phone Outbound Calling API is organized around REST. Our API has predictable, resource-oriented URLs, and uses HTTP response codes to indicate API errors. We use built-in HTTP features, like HTTP authentication and HTTP verbs, which are understood by off-the-shelf HTTP clients. JSON is returned by all API responses, including errors, although our API libraries convert responses to appropriate language-specific objects.
The below diagram outlines a typical case where API is called from your application and how Voice2Phone works in such cases: