[frsyuki]

You can use type-conversion APIs with MessagePack if you use C++, Java or C#. It converts deserialized objects (=dynamically-typed) into statically-typed objects using templates (C++) or reflection + dynamic code generation (Java and C#). You don't have to write boring type-checking codes.

Note that this is a characteristic of the implementation, not of the data format. Some libraries for JSON like JSONIC (Java) provides these APIs.