Is everyone on the team passionate about the idea? Is this a tool you'd like to use yourself?
One of the biggest mistakes startups make is that they start developing something they are not passionate about - because startups like to be in the build-first mindset (slow down!). The reason is that regardless of whether or not the idea will become a crazy money maker, you will be spending more time on it than you have originally planned, because there are no overnight successes. Can you imagine working on a project you are not passionate about for 1-2 years, or possibly more?
This is what happens when you have too much passion
A lot of startups actually shut down their startups because they couldn't stand having to work on something they're not passionate about. This problem is very very realistic, and needs to be taken into serious consideration before you embark onto this long startup journey.