Information about javascript Rendering Template API

Hello,

I was looking information about customization Rendering Template for already existing Callout
I found this article at msdn. The problem is I cannot find any documentation at msdn that describe what we can change in Rendering template and how. The object that apply changes to Rendering Template is JSON object.

SPClientTemplates.TemplateManager.RegisterTemplateOverrides(overrideCtx)

Microsoft does not have this information or this information is not published yet?
As I understand now I need look at callout.debug.js , clienttemplates.debug.js files and try to understand how this rendering works, is that only way now?

http://msdn.microsoft.com/en-us/library/office/jj220045(v=office.15).aspx

(function () {// Initialize the variable that stores the objects.var overrideCtx = {}; // this object does not have any structure description
    overrideCtx.Templates = {};// Assign functions or plain html strings to the templateset objects:// header, footer and item.
    overrideCtx.Templates.Header = "<B><#=ctx.ListTitle#></B>"+"<hr><ul id='unorderedlist'>";// This template is assigned to the CustomItem function.
    overrideCtx.Templates.Item = customItem;
    overrideCtx.Templates.Footer = "</ul>";// Set the template to the://  Custom list definition ID//  Base view ID
    overrideCtx.BaseViewID = 2;
    overrideCtx.ListTemplateType = 10057;// Assign a function to handle the// PreRender and PostRender events
    overrideCtx.OnPreRender = preRenderHandler;
    overrideCtx.OnPostRender = postRenderHandler;// Register the template overrides.SPClientTemplates.TemplateManager.RegisterTemplateOverrides(overrideCtx); 
// this method also dont have any description at msdn also
})();