Json is very nice and flexible but it can be causes for error if you are in a design phase of your protocol.
Therefore It would be handy if you could automatically check if any expected input value and result value is present in the request or the reply.
For this to work you need a definition of the request/reply which could refer to a JSON Schema.
For the request the method name would be perfect.
However for the reply there is no name for the reply type. Therefore I would suggest to add a field 'replytype' which allows for a name that refers to a schema.