I would think an agricultural tool would be made as light as possible...but robust enough to suit its use. Constantly cutting vegetation would be very tiring with a heavy weight blade. Unless this was designed to cut the main trunk of a banana bush (not trees as some people think....in fact banana's are classified as a berry) then my vote is, its a weapon. Bearing in mind the medial ridge would not allow clean deep cuts into 'woody' branches .....human flesh, however, is another story.
Another clue could be the design of the scabbard, it seems to be designed for 'rapid' removal , not necessary for agricultural use.....unless your bananas are particularly aggressive
Regards David