For this Common Form ...

{ "content": [
    { "reference":"Indemnity" } ] }

... an annotation might be ...

{ "message": "The heading \"Indemnity\" is referenced, but not used.",
  "level": "info",
  "path": [ "content", 0 ],
  "source": "commonform-lint",
  "url": null }

Levels

"info" denotes annotations that provide additional information or suggestions, such as to flag an archaism in form text.

"warn" denotes annotations that indicate possible oversights, such as notice that a fill-in-the-blank has not been filled in.

"error" denotes structural or other significant faults in a form, such as uses of terms that aren't defined.