Custom data on membership tab

[Eileen]

Following on from this

http://forum.civicrm.org/index.php/topic,28985.0.html

I want to display custom data below membership type  (much like Dave suggested to do with description for relationship type). I'm going to add it to the tpl (possibly into our repo so all our clients get it - not sure yet) & will add custom fields if they exist for members (with some limits I guess).

So, the question is - can I do an api call to get all custom fields that extend memberships? Do I have to do

custom_group.get->(extends=members)->api.custom_field.get

(not actual syntax but you get the idea)

NB - I thought maybe 'profile.get' would be a good plan - but it is only for contacts