Soundest documentation (API reference) is published here. We like it really much because it's interactive. You can test our API methods before you start coding.
Enter API key (learn how to create an API key) and hit Explore.
Now click on any group of methods. In this example we will choose Campaigns.
A full list of methods will appear.
Let's click on "/campaigns". This methods lets you get all campaigns that you have sent using Soundest. Hit "Try it out!".
This way you will make a real request and get a response with real data from your Soundest account.