TL;DR: If you are getting “No predicate descriptor was registered with Id ‘9f3a44f4-179a-4d19-8583-14a8874e5bba’” in your Automation Engine log, make sure your XML definition file is prefixed with “sc.”   I recently needed to create some custom predicates for Marketing Automation in Sitecore 9.0. Sitecore has made a decent attempt at documenting what you need to do, but it is quite lacking in one specific area. After you have created your new class and inherited from ICondition (don’t worry about IContactSearchQueryFactory. It is not specifically mentioned, but for Marketing Automation rules you only need ICondition) you need to copy the DLL file that contains your custom predicate to the Automation Engine in this location: XConnectFolder\App_data\jobs\continuous\AutomationEngine. You also need to create an XML file for Automation Engine […] Read more