Without a proper description, your potential customers won't know what your application does or have the relevant information to decide whether to install your app or not. Regardless of whether your app is free or paid, the lack of a proper description will be a negative strike against your application.
A simple one-liner won't do it either--you want to convey to your potential customers exactly why they want to download your app. What does it do? What features does it have that will make your users interested in it?
Always take the opportunity to write a detailed description for your application.