I don't know anything about your API but in my personal experience, I tend to prefer APIs where every element is well-named and meaningful. It provides a stronger contract from server to client about the commitment (or contract) to provide data in a certain way. I most enjoy APIs that have strong internal-consistency for naming conventions and defaults, and also a lot of self-similarity so the outputs of one method are easily used as inputs to another.
You can define all sorts of generic container objects that will cover every expected use-case, but you might want to think about the relative importance of flexibility vs. clarity of structure and simplicity, always remembering that flexibility is more expensive (for both sides of an RPC) in terms of code complexity needed to handle the various permutations in which a generic container type might manifest itself. I'm really guessing at your use-case here, though. Can you share some more detail?
