It might be easier, but it's trivial to come up with cases where you cannot generate an example that completely satisfies given JSON schema. It feels like this only works for some specific rigid JSON protocols. You also cannot restrict the types to anything more specific than JSON primitive types.

A "better", certainly more common solution is to generate the type based on whatever source code is generating the JSON, if you have access to it (or have the API provided generate the signature for you).