* `is_html`: *Optional.* Indicate that the input is formatted as html
* `data_file`: *Optional.* (string) Filename to post using a custom_event message type. If unset, defaults to the data_file on the resource. If it exists, the file must contain valid JSON.
* `trigger`: *Optional.* (string) Arbitrary test to add to a "trigger" data item on custom message types.
* `always_notify`: If true, send a notice even if text_file and data_file are empty. If false, and a text_file is specified but empty, a notification will not be sent.