> cbor doesn't prescribe sending schema, in fact there is no schema, like json.

You are right, I must have confused CBOR with BSON where you send field names as strings.

>on top of it, i am saving approx. 20% in message size compared to protobuf bc i am using mostly arrays with fixed position parameters

Arrays with fixed position is always going to be the most compact format, but that means that you essentially give up on serialization. Also, when you have a large structure (e. g. full set of device state and settings)where most of the fields only change infrequently, it makes sense to only send what's changed, and then TLV is significantly better.