I am guessing the assumption is that each service that allows hook specification also identifies the info it would be posting. ie: Enter a webhook you would

I am guessing the assumption is that each service that allows hook specification also identifies the info it would be posting. ie: Enter a webhook you would like to be POSTed to when you receive a tweet. The webhook will be appended with the following url-encoded fields: sender, time, message. Whatever URL you specify as your webhook needs to be able to handle it. The burden is on you to make sure that you integrate successfully with what is being POSTed. It is actually a pretty nice method of ensuring that a service can inter operate with a large number of other systems without the service provider having to know about them all. I don't think the assumption is that you can just enter any old URL and it will magically work. I think the power is behind it is that it is simple enough that: a) any service can trivially implement their end of it b) anyone interested in extending the service can trivially implement their end of it I'm sure someone doing part b will decide they need to take the post and form an XML message and relay it to a web-service, but it isn't really necessary.