This document gives a basic understanding of the API, though you may want to see which API calls Tower makes in sequence. To do this, you can use the UI from Firebug or Chrome with developer plugins.
Another alternative is Charles Proxy (http://www.charlesproxy.com/), which offers a visualizer that you may find helpful. While it is commercial software, it can insert itself as an OS X proxy, for example, and intercept both requests from web browsers as well as curl and other API consumers.