kind property
Kind is what looked wrong: outlier (a charge far above the usual), reversal (a posting undone), roundoff (a balancing plug big enough to be worth explaining), uncosted (revenue booked with no cost matched to it), or overdrawn (a wallet spent past its balance).
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? kind;