You can also check the weight. Carbide is heavy. Also the corner of a file will skip across carbide like it was glass. And the color of carbide is duller than the shine of HSS.
About the only solid carbide cutters will be straight spiral cutters, the rest will have a piece of carbide silver soldered to a steel body of the cutter. The solder joint between the carbide and the tool body is easy to distinguish.
Thanks,
Chuck