Identifier of the mailing list to which the subscriber will be added (optional). Required in practice — omitting it causes failure even when a default list exists.
customfieldsarray
Custom fields for the subscriber as an array of objects with customfield_key and customfield_value (optional). Only predefined custom field keys are accepted. Unrecognized keys are silently ignored — no error is raised, and the data is dropped.
Observable output
data
Required
Data from the action execution
errorstring
Error if any occurred during the execution of the action
successfulboolean
Required
Whether or not the action execution was successful or not