This includes hard-errors like 404 and 500s, but also soft-errors such as validation errors, which give a breakdown of the individual attributes and why the data was invalid.

Hard Errors (404s / 500s)

{
  "error":"not_found",
  "error_description": "We couldn't find the page you were looking for."
}

Soft Validation Errors

{
  "error": "invalid_resource",
  "error_description": "The current resource was deemed invalid.",
  "messages": {
    "name": ["can't be blank"],
    "support_telephone": ["can't be blank", "is not a number"],
    "support_email": ["is too short (minimum is 5 characters)", "is invalid"]
  }
}