I downloaded and installed Esenthel but i can't find the API reference.
Is it only provided for Licensed developers ?

http://www.esenthel.com/wiki/index.php?title=Main_Page

there is the Wiki as Dynad said, there is also Documentation.chm in the EsenthelSDK folder which is basically the same as Wiki, and there is HeaderBrowser tool in the EsenthelSDK/tools, and it is possible to browse through the headers with visual studio

http://www.esenthel.com/wiki/index.php?t...ction_List

Yes, I read the documentation and I already used the Header Browser tool but I'm actually used to the *nix development environments where the API reference is often a simple well structured documentation generated using Doxygen. I recommend Esenthel to use it BTW.