Thinking about APIs, part 2

In Thinking about APIs I talked about the common problem of coupling between a client application and a server, via their shared knowledge of resource URLs:

As I noted in that previous article, and as @Ivan pointed out in the comments, this is exactly analogous to a local function call, in that both the client and the server need to agree on the resource path (Connascence of Name) and the structure of the call and its response (Connascence of Type?).

But what makes this problem a real challenge — ...