How are attempting to set the property? And how are you defining the scripting API for DevonThink? Assuming you've got the right API mapping, properties cannot be set directly — you have to use their corresponding setter method, e.g. setName(_ name: String). For example: let url = URL(fileURLWithPath: "/System/Volumes/Data/Applications/DEVONthink 3.app") guard let application = SBApplication(url:url) else { return } let devonThink = application as DevonThinkApplication // Change name of the currently selected record let currentRecord = devonThink.contentRecord currentRecord?.setName?("new-name.md") If that's not working, then the scripting API was defined incorrectly.