An out-of-band type specifier would be cool, though you still have to know the implicit schema implied by each type. In the system I work with, we standardized

An out-of-band type specifier would be cool, though you still have to know the implicit schema implied by each type. In the system I work with, we standardized on objects that have a "type" key at the top level that contains a string identifying the type. Of course, that only works because we have lots of different tools that all output the same 30 or so data types. It definitely wouldn't scale to interoperability in general. But that's also one of the great things about JSON: it's flexible enough that you can work out a system that works at your scale, no more and no less.