Can I add hyperlinks in link descriptions?
Sure! You just need to add the relevant HTML markup directly within the L&L description box. In fact, you can add any HTML markup within the description box - so you can bold/italicize text, add an image, etc.
The caveat is that you still must adhere to the 500 character maximum within that box - so if your links are particularly long, you might consider using a URL shortening service (such as bit.ly) to conserve space.
And you'll get this (note, the text in blue is hyperlinked):