What I said: it looks at the whole story, rather than piecemeally stitching together a stack. The downside is that it's maybe overwhelming, especially with multiple competing protocol specs and stacks doing the same thing.
As to XML: IMHO actually XML isn't a good fit for most API payloads. XML comes from markup languages/SGML which model semistructured data as regular content models, rather than co-inductive data structures of programming languages. The thing is, though, that the alternative, JSON, is really too basic (doesn't have schema-based validation, doesn't have date datatypes or enumerations, hell doesn't even have decimal numbers, etc.) Part of the story why JSON is so popular is that it's untyped and you don't have to agree on schemas, typed payloads, etc. upfront, and can just begin coding - but that also means you don't have typing, service contracts, etc. as your apps mature.