Hi,
description, historicalInterval and perfCounter are the properties of PerformanceManager managed object. In order to retrieve these properties, you need to invoke RetrieveProperties method,of PropertyCollector, which retrieves the specified properties of the specified managed objects.
Please refer to the vSphere Programming guide, section 8 Obtaining References to Objects and Property Values from the Server(pg 73), on how to use RetrieveProperties method. http://www.vmware.com/support/developer/vc-sdk/visdk400pubs/sdk40programmingguide.pdf
Hope the information is helpful
You might also want to have a look at the VI SDK PropertyFilter - Getting Started Community Guide, which explains on how to use propertyfilter object and to use retrieveproperties method. http://communities.vmware.com/docs/DOC-9499