Currently, there is no way to add a description for a Task. Internally, we found that a description on a task was not useful and if we needed a description we were usually better served to break that task into multiple tasks or even stories. However, I can think of scenarios where a description may be helpful, especially in a more distributed team. I have added your suggestion to our backlog and it will be considered for future releases depending on how popular this request is.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items