Deprecating a field with a header and a date

Removing a field from an API response needs a period where consumers can see it is going, and a way to know whether anybody still reads it.

HTTP/1.1 200 OK
Deprecation: Sat, 30 Sep 2023 23:59:59 GMT
Sunset: Tue, 02 Jan 2024 23:59:59 GMT
Link: <https://docs.example.com/api/orders#total>; rel="deprecation"

and the part that does the work: logging which client ids
requested the field, so the removal date is a decision
rather than a hope.

The headers are standard and largely ignored, which is why the log matters more: three months of “who is still asking for this” turns a removal into a conversation with four named consumers instead of an announcement to everybody. Two of ours had stopped using it years earlier and were still requesting it because the field was in a serialiser nobody had revisited.