Considering Oracle 12c was supported at ArcGIS 10.2.x (I think it was starting from 10.2.1), the 10.2.2 SDE Command line tools should work for the Oracle 12c databases at version 10.3. Its been sometime that I needed to use the SDE Command line tools, so I don't remember it exactly.
This link ArcSDE application server for Oracle installation guide mentions that
There is not a separate installation for Oracle 12c. Use the ArcSDE Application Server for Oracle 11g installation.
Maybe a quick call to Esri Tech Support and they can show you.