When the inbound rule triggers an action the action gets the payload from the incoming request as the input variables. These can be used to create/update issues, to determine what variables is available you will need to inspect the incoming payload.
The incoming payload is seen both in the Inbound Log view and the Execution Log
Let´s view the scenario where GitLab POST a comment from a GitLab issue to iHub incoming rule engine. Read more here Inbound Integrations
The payload can then be viewed in the Inbound Log like below
Here we see that Action Create GitLab Comment Issue has been triggered. Clicking the View button we can inspect the payload.
Inbound View payload.
This is also shown directly on the Action it self in the Execution log by clicking the View button in the list.
Execution log view
Image above shows an Incoming Payload of an action that comes from a triggered rule from the Execution log. Once a incoming payload is associated to the action it will be displayed in the Incoming payload section of the execution log entry.