The Slicer cli modules have xml files describing their parameters. These values should all flow through to the module documentation on the wiki.

For example, in the simple region growing segmentation module, there is a parameter called inputVolume, but this exact string does not show up in the module documentation (I had found the source xml file randomly before and can no longer find it). The exact string name that must be passed for this parameter should be displayed on the module wiki page.

http://www.slicer.org/slicerWiki/index.php/Documentation/Nightly/Modules/SimpleRegionGrowingSegmentation