Link relations can be designed that indicate which HTTP methods are allowed. HAL is heavily dependent on conveying semantics via link relations, which is something that some people don't like doing.

Consider the oauth2-token link relation defined here[1]. The definition of this link relation refers to RFC 6749 [2] which states that it is necessary to pass a application/x-www-form-urlencoded body using POST.

[1] https://tools.ietf.org/html/draft-wmills-oauth-lrdd-07#secti... [2] https://tools.ietf.org/html/rfc6749#section-4.1.3