Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Mode
TOOL_MODE_INTERACTION
Parameter: Radius
TOOL_PLACEMENT_OUTER_RADIUS
Parameter: Object Spacing
TOOL_EXCLUSION_RADIUS
Parameter: Use Splats
TOOL_USE_SPLATS
Parameter: Splat Spacing
TOOL_INTER_SPLAT_SEP_DISTANCE
Parameter: Count
TOOL_PLACEMENT_ATTEMPTS_PER_SPLAT
Parameter: Density
TOOL_PLACEMENT_DENSITY
Parameter: Source
TOOL_MODE_OBJECT_SOURCE
Parameter: Random Order
TOOL_RANDOMIZE_ORDER
Parameter: Seed
TOOL_RANDOM_SEED
Parameter: Align To
TOOL_MODE_ALIGN_TO
Parameter: Reference Point
TOOL_ALIGN_REFERENCE
Parameter: Position Min/Max
TOOL_MIN_MAX_Y_OFFSET
Parameter: Rotation Range
TOOL_ROTATION_RANGE
Parameter: Scale Min/Max
TOOL_MIN_MAX_SCALE
Parameter: Show mouse region preview
TOOL_SHOW_PREVIEW_REGION
Parameter: Show Placements
TOOL_SHOW_PLACEMENTS
Parameter: Show Splat Regions
TOOL_SHOW_SPLAT_REGIONS
Parameter: End Stroke
TOOL_BUTTON_END_SESSION