Going to the Wire Styles (Project>Configuration>Wire Styles) and clicking on a wire's properties allows you to populate whatever fields you desire. In this case, Description isn't available as an attribute (in 2015), don't know why. So instead, you can change your User Data fields, in this case I renamed it "SPEC" and populated the field.
Then you can customize which attributes of your wires show by going to (Project>Configurations>Project Configuration>Graphics tab>Wire_Label (edit icon)
The actual "Description" field isn't available as far as I can see but you can customize either user data field to be called whatever you want and included in your attributes.
You are right , unfourtunately this is an SPR.
I wish SW put there a description attribute
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