Before you query anything, it helps to know how Fulcra structures what it holds: what a record is, what a data type is, and how the pieces relate.
There are only a few concepts and they don't change often. A data type describes the shape of something you can record. A record is one entry of it. Records are either events, covering a point or a span of time, or metrics, covering a value over time. Every record carries where it came from, and records can be tagged.
Everything you read or write sits inside that model, including data types you define yourself.
Full details are in the developer documentation: