Im trying to calculate geometry in python for a script tool for arcmap.

For the script i want to calculate area in hectares. I am trying to use the add geometry attribute (data management) tool, but its not working and its giving me all 0's in my output field. this is what I have:

# Set Calculate geometry variables

calculate_table = clip_output

geometry_prop = "AREA"

expression = "HECTARES"

# Run calculate geometry
arcpy.AddGeometryAttributes_management(calculate_table, geometry_prop, "", expression, "")


whats wrong?
should i use a different tool?