Since Beaker 0.15 for new client commands we have been adding "private"/undocumented HTTP APIs in the RESTful style, rather than continuing to add more XMLRPC methods.
Now that those APIs have been stable for a few releases (and are beginning to be used in spite of their undocumented status) we should document them and make them officially stable.
I think the only ones we have so far in 0.17 are:
There are a bunch more which will be added for new-system-page (bug 1014438) as well.
As folks are starting to use these now, it would be good to get them properly documented for Beaker 19.
New server API docs are visible here:
Beaker 19.3 has been released.