Callpoint in yang model

Hi,
we were running the example simple_notrans.
The original yang module has call point as follows:
/* A set of server structures */
container servers {
tailf:callpoint simplecp {
}

when we run this example we got:
isim@gamba> configure
Entering configuration mode private
[ok][2016-08-03 13:52:55]

[edit]
isim@gamba% set servers server
Possible completions:
name:string
isim@gamba% set servers server gg ?
^
% Invalid input detected at ‘^’ marker.
isim@gamba% set servers server gg ?
^

we removed the call point from the yang model and build it again. now we were able to configure the sample:
isim@gamba% set servers server
Possible completions:
name:string
isim@gamba% set servers server gg ?
Possible completions:
ip port
isim@gamba% exit

Since we are working with external CB, we must have call points in our yang models.
Please help me understand how to configure with the call point.

thanks
Inbal

It looks like you may only be running the confd daemon but not the data provider client application. Have you started the client application named simple?