A cable tester is specifically designed to check the electrical connections and continuity within an Ethernet cable. It can ensure that each wire is properly connected to the corresponding pin on both ends of the cable, which is critical for network functionality. Other tools listed are incorrect as their functions do not include testing the wiring and pin connections of Ethernet cables. A multimeter measures electrical properties like voltage and resistance, not pin-to-pin continuity. A cable crimper is used to attach connectors to the ends of cables, not to test the connections. A tone generator identifies wires in a bundle but doesn't check for proper wiring of an Ethernet cable. Punchdown tools are used for connecting wires to patch panels and similar blocks, not for testing cables.