The API used only supports supplying action name and note. If you use the Clip-o-tron facility, you can have actions go to the Quick Entry box instead of directly into the Inbox, which offers you the chance to set project, context, dates, and edit action name and note before saving. Personally, I tend to let them accumulate in the Inbox (especially since where there's one thing I want to read later, there's likely to be another) where I can select several actions at once and use the Inspector to set project and context simultaneously. I do this even though I have clippings initially go to the Quick Entry box. Just seems to end up being a bit less work overall, YMMV.