g.command 'add' do |c|
          c.flag 'external_unique_id', desc: 'An ID supplied by the 3rd-party Call provider. It must be unique across all Calls from that service.'
          c.flag 'join_url', desc: 'The URL required for a client to join the Call.'
          c.flag 'created_by', desc: 'The valid Slack user ID of the user who created this Call. When this method is called with a user token, the created_by field is optional and defaults to the authed user of the token. Otherwise, the field is required.'
          c.flag 'date_start', desc: 'Unix timestamp of the call start time.'