The third question is to ask if this Online Tool will create additional barriers to accessing or learning the information. Access is an important consideration. Don't assume we are all tech savvy, don't assume we all have the latest high-tech devices and software. If you do, you risk disenfranchising those of us who lack the funds or inclination to have the them. I'll bet that iPhones and PDAs have a higher penetrance among teaching faculty than among students.
Also make sure your students can find your tool easily. By that I mean it really needs to be a single click away from your course page. Having to register and log-on at an external site, even if it's free, creates a barrier. A requirement to download certain software or *gasp* pay even a few dollars for access, will significantly reduce the exposure your tool gets to your audience.
Another important consideration is cognitive load which, crudely put, refers to the amount of novel information that is presented simultaneously. When the cognitive load is too high, it overwhelms working memory and impedes learning. When it is too low students will have difficult keeping their attention on a task that seems tedious and is telling them what they already know. An appropriate cognitive load is highly dependent on the individual student's prior knowledge and is admittedly difficult to match to an entire classroom. Scaffolding is one way to get around this, but it is beyond the context of this module.