Request headers

Content-Type:

Specifies in which media type the request is expressed. Recommended value, unless stated otherwise for specific rels: application/hal+json

Content-Length:

Required by HTTP when sending a payload.

If-Match:

Required when updating a resource. See individual Rels for which requests require it. The value comes from the ETag header of a relevant response.

Accept:

Expresses in which media type to return the response. Recommended value, unless stated otherwise for specific rels: application/hal+json

Response headers

Content-Type:

Specifies in which media type the response is expressed. Will attempt to conform to the request's Accept header through appropriate content type negotiation.

Content-Length:

Required by HTTP when returning a payload.

ETag:

Value to be used in a subsequent request updating the resource. See above: Request headers> If-Match.

Link:

If present, is usually rel of the response.

Cache-Control:

Currently used internally. May be expanded in the future for external use.