AME Transaction Type Setup

We would like to create new transaction types in AME that relate to transactions in other Oracle EBS modules (Release 12.1.1).  When defining the transaction type, the modules we are interested in are available in the LOV for Applciation.  It looks to me as though the "Transaction Type Key" should be used in conjunction with the Application to "link" AME to the appropriate module and transaction. 

The problem is that I cannot find any references as to how to determine the appropriate "Transaction Type Key" for a given transaction or object in another EBS module.  The field is free-form text, and the documentation simply says "Enter the transaction type key and name.  Typically, these properties must identify the nature of the transaction."