Why am I getting an HTTP 400 error when including an Event Log of Transaction Complete in my Engagement Engine Rule?

Environment:

Engagement Engine
Engagement Engine Inspector

Issue:

I'm receiving an HTTP 400 error (within the Engagement Engine Inspector) when including an Event Log of Transaction Complete in my Engagement Engine Rule?

Resolution:

Transaction Completed should only be used for Return on Investment (ROI) purposes and needs to include a Custom Data action (Add Action: "RightNow Custom Data: Populate with Value") within the rule as well.

It's considered a Convert (conversion) Event. Per ROI Reporting document, "A convert event is sent to the server whenever a visitor has performed an action that has some value to the customer. Note that the conversion event is completely defined by the customer through the Engagement Engine rules editor."

For additional information, refer to What are some popular Business Rules in Engagement Engine?  Within the attached PDF, refer to "Conversion Tracking Rule" on page 6.