Why eventAttendanceMode needs the full schema.org URL#
eventAttendanceMode is not free text — Google expects one of three specific values, each the full https://schema.org/... form (OfflineEventAttendanceMode, OnlineEventAttendanceMode, or MixedEventAttendanceMode), not the bare word. Typing the short form is a common source of Event schema that looks correct but fails validation. This tool sets the correct full-URL value automatically based on whether you picked a physical or online location, so you never have to type it by hand.
Place versus VirtualLocation — schema.org's two answers to "where"#
A physical event's location is a Place — a named venue, ideally with an address. An online event's location is a VirtualLocation — the URL attendees actually use to join, not a physical address at all. These are structurally different objects with different required fields, which is why this tool asks a location-mode question up front rather than trying to guess from a single generic "location" field.
Why the image is required, not optional#
Like Article schema, Event schema without an image is not eligible for most of the rich-result surfaces Google actually offers for events — a listing with no visual is far less useful in a search result. This tool treats the image as required rather than a soft recommendation, for the same reason it does on Article Schema Generator.