IssueTracker

It would be nice if Google Cloud Endpoints would allow developers to specify a different JSON Serialization/Deserialization mechanism (e.g., Jackson 2.x) as opposed to the baked-in version.  

Currently, class models that use the @ApiTransformer annotation pointing to a transformer that implements something like com.google.api.server.spi.config.Transformer<MyModelType, String> become ineligible for use as an Endpoint method return type (no String, enum, or primitive is allowed).  

So, it seems like developers have very little control over the JSON mapping of endpoint representations aside from changing the name of a property and/or ignoring it.