You kind of need to make a basic pitch at least, so people get a basic idea of what to expect beyond the main concept.  Otherwise, it's going to be hard for them to express interest since... There's nothing really to express interest in. ^^;

Take a look at some of the other interest checks, especially the ones in casual if that's how you're intending to run this.  It'll help you get an idea of what you need for an interest check.