Get events and registered order books, including scheduled events with no books. event_ids and market_ids accept up to 50 comma-separated positive IDs, are mutually exclusive, and use the same filters, sorting and pagination. market_ids returns each related event once with all its order books. Defaults to descending id. start_at sorting uses (start_at, event_id); cursor identifies an existing event and excludes it in the requested direction. tag filters across creators; creator_account_index is an optional additional filter. active=true requires a tradeable outcome; active=false includes scheduled and closed events.