Hello SharePointer :),
These days I am working with SharePoint 2013 master page and I see that, site description is not available, however we can display that using inbuilt SharePoint webcontrol control
just place below lines on your html master page where your div is looking for site description :
<!--MS:<SharePoint:ProjectProperty Property="Description" runat="server">--> <!--ME:</SharePoint:ProjectProperty>-->
And you will see all pages with site description.
Happy SharePointing !