Every time there's a new post about GraphQL, I become even more concerned that "GraphQL" was the wrong name to use publicly. It seems like most people assume it's just another combination of two buzzwords, Graph and QL, and incorrectly pattern match it.
In an attempt to help resolve this issue, I suggest that you think of it as ProductQL or ProductAPI instead.
It's not a storage layer. It's not really a query language. It's an alternative way to define an API that more closely matches the typical mental and product domains than REST.
It's critical to realize that you're implementing an API. GraphQL does not concern itself with sorting or fetching data as the name might lead you to initially believe. It has little to actually do with graphs (except they are more easily expressed). It is designed to be added on top of your application layer and business logic to provide a single, well defined API for your product and tools.
It primarily targets product developers. From the scheme/API side, it is up to the server developer to decide what to expose and how, based on the product and any technical considerations that need to be made.