ApiError

The shape of a refusal from the klock v2 surface, and of every newer
route: a stable machine-readable error code and a human message.
Some refusals add fields — needs and unlock on a capability refusal,
reason on an ended session. (Older routes answer { error } with a
sentence in error; see Error.)

{
    "error": "capability_missing",
    "message": "This session cannot do that",
    "property1": "string",
    "property2": "string"
}