Need a divorce agreement before filing for uncontested divorce?

My ex and I are splitting up and we agree on how to divide everything. We don’t have any kids. I don’t want to spend a lot on legal fees so I went to the courthouse in Clark County to file. The clerk told me I needed a written agreement stating what my ex and I have agreed on before I can file the uncontested divorce papers. I don’t know why we need this if we don’t dispute anything. What do I need to do to get the written agreement and what should be in it? Do my ex and I have to both sign it in front of a witness or a notary?