Summary
The Describe function returns the following properties for Relationship Classes. GDB Table Properties, Table Properties, and Dataset Properties are also supported.
A Relationship Class returns a dataType of "RelationshipClass".
Properties
| Property | Explanation | Data Type | 
| backwardPathLabel (Read Only)  | The backward path label for the relationship class.  | String | 
| cardinality (Read Only)  | The cardinality for the relationship class. 
  | String | 
| classKey (Read Only)  | Class key used for the relationship class. 
  | String | 
| destinationClassKeys (Read Only)  | A list of tuples, with the object key name, and key role (DestinationPrimary, DestinationForeign).  | tuple | 
| destinationClassNames (Read Only)  | A list containing the names of the destination classes.  | String | 
| forwardPathLabel (Read Only)  | The forward path label for the relationship class.  | String | 
| isAttachmentRelationship (Read Only)  | Indicates if the relationship class represents a table attachment.  | Boolean | 
| isAttributed (Read Only)  | Indicates if the relationships in this relationship class have attributes.  | Boolean | 
| isComposite (Read Only)  | Indicates if the relationship class represents a composite relationship in which the origin object class represents the composite object.  | Boolean | 
| isReflexive (Read Only)  | Indicates if the origin and destination sets intersect.  | Boolean | 
| keyType (Read Only)  | Key type for the relationship class. 
  | String | 
| notification (Read Only)  | The notification direction for the relationship class. 
  | String | 
| originClassNames (Read Only)  | A list containing the names of the origin classes.  | String | 
| originClassKeys (Read Only)  | A list of tuples, with the object key name, and key role (OriginPrimary, OriginForeign).  | tuple | 
Code sample
The following stand-alone script displays properties for a relationship class.
import arcpy
# Create a Describe object
#
desc = arcpy.Describe("C:/data/moad.gdb/West/bapCompAttRel")
# Print relationship class properties
#
print "%-25s %s" % ("Backward Path Label:", desc.backwardPathLabel)
print "%-25s %s" % ("Cardinality:", desc.cardinality)
print "%-25s %s" % ("Class key:", desc.classKey)
print "%-25s %s" % ("Destination Class Names:", desc.destinationClassNames)
print "%-25s %s" % ("Forward Path Label:", desc.forwardPathLabel) 
print "%-25s %s" % ("Is Attributed:", desc.isAttributed)
print "%-25s %s" % ("Is Composite:", desc.isComposite) 
print "%-25s %s" % ("Is Reflexive:", desc.isReflexive)
print "%-25s %s" % ("Key Type:", desc.keyType)
print "%-25s %s" % ("Notification Direction:", desc.notification)
print "%-25s %s" % ("Origin Class Names:", desc.originClassNames)