Hi Bernd,
I think it would be nice to have the possibility to provide a detailed error report.
Yet, I am not sure if a String field is the best solution. Depending on your scenario, the error report may have a structure and that structure could be processed automatically (e.g. a JSON object that identifies the machine that processed the external task, its workload when the error occurred, etc.). In such a case, providing a TypedValue (e.g. Spin JSON) would be much nicer.
Not sure how that would work together with a generic Incident application that displays errors for both jobs and external tasks, but from the external task perspective I would prefer that.
The poor man’s alternative to that could also be allowing variables to be submitted on the handleFailure call which can contain any error information.
Cheers,
Thorben