Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Create Tri-/Quadrangle
MDATA_ADDPOINT_TRI
Parameter: Polygon Type
MDATA_ADDPOINT_POLYTYPE
Parameter: Edge Position
MDATA_ADDPOINT_EDGE
Parameter: Position World
MDATA_ADDPOINT_POSITION