The link manager was removed from WordPress in version 3.5; but the base level code is still present, and can be enabled using the Link Manager plugin.
If you have the link manager available, you can use these fields to configure Tweets when you add a link to your blogroll or another list of links. Because links don’t use the same meta data that’s available for posts, the template tags are different. You can only use #title#, #url#, and #description# within link templates. Your link will be shortened using the same URL shortener you have set up for your other status updates.