I've got a 9 1/2 foot X 7 foot deck and didn't have any where to carry tools......go figure!
Ended up hanging a couple of under-deck boxes. Powder coated with SS doors. Inside the left one is a complete set of 3/8 and 1/2" drive socket sets, a set of combinations, box ends, and assorted screw drivers. A hydraulic jack, jack stands, jumper cables, 12V trouble light, rags, 2 qts of oil, some empty coffee cups, and probably some empty soda cans.
The right one has a bunch of cleaning stuff, two gallons of water, a tow chain, tie-down straps, and misc stuff.
I was in the check-out at Lowes several months ago and they had some self-stick battery powered LED push-on, push-off lights. $6.00 each. So I bought one for each box and they do a great job lighting up the inside of the boxes at night.
I don't carry the stuff for myself as much as just being prepared. You never know. I hear someone saying..." it's killing your mileage"......what mileage?