clean JSON
  is_unknown   false
  question     Does it have whiskers?
  yes_is       a cat
  confidence   unknown
  is_unknown   true

JSON buried in prose and fences
  is_unknown   true
prose instead of JSON
  is_unknown   true

bad first, good on the retry
  (asked once, and answered in prose)
  (asked again, this time with a correction)
  is_unknown   false
  question     Does it have whiskers?
