Precise definition of term: *schema*
In order to write the documentation of the structure of the JSON objects returned from your API you can follow two approaches:


describe the common attributes and of the objects returned by every function of your API; and then for each API function describe the specific attributes (their type, meaning, and example);
Many APIs that use JSON to exchange data are documented using this approach: e.g. Google APIs for various services, Facebook Graph API, Twitter API, ...
In this case I think it is not correct to use the term "schema".
or you can give a formal description of the output using a schema definition language like JSON-schema (designed by the IETF) and that plays the same role of the XML schema definition language for XML.
But I don't know if JSON-schema is an established standard (there is an active Google group, but I didn't find any "notable" example, ... ).
In this case you should provide a valid (json-)schema for the output of each function.

If you choose this approach, then you should say that name and age are two required properties of the (json-)schemas of the (json-)objects returned by the functions of your APIs (but obviously you should provide the full-schemas, too)