How can I enable the API plugin debug?

Below is a snippet of a probe's configuration with the API plugin included:

Below is a sample debug output:

<Tue Mar  5 10:47:55> DEBUG: API:manager Trying to find sampler 'sles10.XML-RPC'
<Tue Mar  5 10:47:55> DEBUG: API:manager Calling function 'createView' on sampler 'sles10.XML-RPC'
<Tue Mar  5 10:47:55> Vector::show() 0xbfd68670; vector contains 2 entries, buffer: 8
<Tue Mar  5 10:47:55> {
<Tue Mar  5 10:47:55> Index 0:
<Tue Mar  5 10:47:55> String::show() WHOLESALE_SSP_MAP 0xa4120f8 17
<Tue Mar  5 10:47:55> Index 1:
<Tue Mar  5 10:47:55> String::show() XML-RPC 0xa3e6330 7
<Tue Mar  5 10:47:55> }
<Tue Mar  5 10:47:55> DEBUG: API[XML-RPC]:exec Executing Sampler method 'createView'
<Tue Mar  5 10:47:55> DEBUG: API:return String data being returned to client: OK