The goal is to build for the smallest problem to start.
Now I want you to further narrow your focus. I want you to look at a few tools that already exist that you could use. Have you already tried solving this problem yourself? What are you lacking with your current solution to this problem? What is it about the other solutions out there that doesn't solve your problem adequately? Maybe they have too many features. Maybe the UX is hard to navigate. Maybe you need more ways to analyze the data. Maybe they only have mobile apps but you want to use it on desktop. etc.
Come up with a few options to solve this problem that exist already. What do you like about them? What falls short? This will further narrow your focus on the problem. How can you build something that makes up for these other tools shortcomings?
Take some time to do this analysis and write it up in a document. You can do it however you like. You can come up with a few criteria to judge existing solutions on and display the comparison in a table, or just do a plain write up in a google doc or whatever. But by doing this your project requirements will start to take shape.
I've seen it time and time again, people building projects without a very narrow and focused vision, and the project either gets scrapped halfway through implementation, or it tries to do too much and becomes unusable. Building software is relatively easy. Building high quality useful software is the challenge.