What is the most efficient and correct way to check that some class can be serialized/deserilized using kotlinx.serialization Of course for simple cases you can check presence of annotations using reflectsions (also would be good to avoid, at least provide some conventional way). What about complicated ones (external serializers etc)? My use case that I would like to adopt kotlinx.serialization but we have a lot of existing data modesl and use Gson for Json mapping, so it would be hard to migrate everything at the same time I’m looking for some migration strategy, one of them to use Gson only as fallback during migration phase

Well, external serializers are also plugged in via annotations or into the SerialContext, so you probably should dig in that direction