* Mike Kelly (the author of the HAL spec) is not aiming for a universal API client http://news.ycombinator.com/item?id=4949357 (and also seems to be under the impression that no-one else is either).
* A universal client seems impossible because APIs will typically need to use service-specific link relations for all "interesting" relations (e.g. product, author). You might be able to share generic link relations (like those in IANA's table: http://www.iana.org/assignments/link-relations/link-relation...), but sharing only these doesn't seem to be worth the effort.
* Hypermedia-powered experimentation is kinda cool, but you're still going to need something to drive it (see e.g. Kelly's HAL browser http://haltalk.herokuapp.com/explorer/hal_browser.html#/), at which point you might as well write a full-fledged API dashboard.
HTML is a hypermedia media type. A server spits it out, the client (a browser) consumes it.
A browser is a generic hypermedia API client, for services that expose HTML.
> it's not an API in the sense most people understand
Neither are hypermedia APIs in general.
How can I point the HAL browser at foxycart's API? Or even see Foxycart's browser? I can only find standard hand-written documentation.