Smarts - 10.1.x
TCSA - 2.x
InstrumentedBy lists the instrumentation objects Smarts uses to poll status information from the SNMPAgent on the device. Each Instrument class/object polls different MIB to gather data. Instrument is like a tool to collect and organize information.
For example, in Smarts the information needed would be Interface Adminstatus and Operstatus which are used to determine if an interface is down or up.
Instrumentation object/class will poll this data periodically and keep statistical information on when this information was polled, when it should be polled next and the current status.