Unified API advice, maybe?

I’m a marketing guy who’s diving into the world of software development, and I’m finding the integration process a bit of a slog. I’m comfortable with OAuth and REST APIs, but getting the exact required fields for each app is still a headache. I’m currently looking for Calendar, billing, and chat integrations for a professional engineering app, and it seems like with unified APIs, you’re either in luck that they do what you want or left out in the cold. I’d like to be able to set up custom configurations that impact how the information is served up. For example, being able to filter data in interesting ways instead of having to get all the information and then use server resources to sort through it. The solution should be scalable, so it can grow with the app as we add more features and users. Scalable probably isn't the right word but basically let's say a Unified API did do everything I need; that's not really a guarantee that it will do the things I need in the future. It seems like this should be possible, right? Has anyone found a tool or platform that makes this process smoother? What I'm guessing is that there a category that isn't Unified API that I'm just not aware of bc software development isn't my forte or that Unified API isn't exactly what I think it is and I'm just not finding the parts of the program that do what I need it to do. Also, these discussion boards seem dead but hoping that the lack of discussions speaks to the fact that most people know what they are looking for already and not bc nobody has time to respond. If I don't have any luck I'm planning on replying to my own thread confidently about the solution that I found (and it will be horribly incorrect.) No faster way to get a correct answer then post the wrong one :) Thanks in advance! edit: can't find a way to add line breaks. wooF! edit2: looks like I might have posted this in the wrong place?