What are the different API error response types and how to understand them?

[seismo]

Hi, in the documentation for Status and Error Codes  different response types are listed for different status codes. For all codes it's a string in the "errors" field, e.g.:

{
  "errors": "Not Found"
}

Except for 422 where it is a list of strings, e.g.:

{
  "errors": [
    "The fulfillment order is not in an open state."
  ]
}

However, In the more detailed section of the documentation  about status codes it says about 422:

The response body provides details in the errors or error parameters.

How do I know when do expect which and what standard can I rely on. Is there a full comprehensive list of all possible error responses somewhere? Dynamically checking for all possibilities is pretty cumbersome and error prone.