I think it depends a lot on why the operation failed and what you need the client to do next. If it is something the client can fix, I think it is reasonable to

I think it depends a lot on why the operation failed and what you need the client to do next. If it is something the client can fix, I think it is reasonable to respond with the appropriate 4xx series status and enough to detail that they can correct and proceed. Same with 5xx series and issues that are out of the client's control. There are other approaches that are more or less as valid. The important thing is that we return enough information for the client to proceed. Wether that is signalled through status codes, headers, or response body isn't as important in my opinion.