Database
[{_id:1,traits:{Rarity:{infoin:15,},Type:{iron:3,sliver:5,wood:7,},},},{_id:2,traits:{Cloth:{barron1:11,barron2:12,},Hair:{black:6,yellow:9,red:8}},}]
Query
db.collection.aggregate([{$set:{traitObjs:{$objectToArray:"$traits"}}},{$set:{firstTraitValues:{$objectToArray:{$first:"$traitObjs.v"}}}},{$project:{traits:{$reduce:{input:"$firstTraitValues",initialValue:0,in:{$sum:["$$value","$$this.v"]}}}}}])