[krainboltgreene]

> With a standard REST interface

There's no such thing.

> you have to name all such combinations in advance.

No you don't.

> Possibly build custom code for each.

As much as any other API.

[imauld]

There is a "standard" REST interface described in the paper on REST. There are a lot of rules/guidelines for a RESTful API but many API's don't follow them and tend to be a mix of REST and JSON RPC.