One of the most important part of any paper, including Descriptions, is your thesis. This should be a single sentence which starts off your description in a way that draws readers (and potential players) in to read the rest of your description while plastering a quick and effective "happy" image of your server into their heads.
A good way to start a thesis is just picture your server in your head and make a sentence starting with "my server is..." don't give this sentence too much thought you want it to be what comes to mind when you think of your server. For example, lets say the server is a community based survival server where your all about making friends with every player and playing together; your sentence would be something like "my server is a community based survival server with no griefing." it's not the actual thesis but its good to build on.
The next step to building a strong thesis is adding a "hook". This needs to be a way to draw readers in and make them want to read the rest of the description. This means make the thesis something that makes the server sound appealing by using more positive words and highlighting the better aspects of your server. A good thesis should be positive and to the point while not going on too long.