AWS Step Functions
Developer Guide

Fail

A Fail state ("Type": "Fail") stops the execution of the state machine and marks it as a failure.

The Fail state only allows the use of Type and Comment fields from the set of common state fields. In addition, the Fail state allows the following fields.

Cause (Optional)

Provides a custom failure string that can be used for operational or diagnostic purposes.

Error (Optional)

Provides an error name that can be used for error handling (Retry/Catch), operational, or diagnostic purposes.

Because Fail states always exit the state machine, they have no Next field and don't require an End field.

For example:

"FailState": { "Type": "Fail", "Cause": "Invalid response.", "Error": "ErrorA" }