It's nice to have tools, but chances are, you'll need a part as well and if you don't have that part....the tools won't help much.
For me, along with a few tools, I like to carry things like two part epoxy or JB Weld, in hopes that I can possibly repair a broken bracket, or whatever and limp home.
I also carry a few hose clamps, and a few small pieces of flat stock steel around half to one inch wide, an .125" thick and from a few inches to a foot long. I can "HOPEULLY" use these along with JB Weld and hose clamps to kinda sorta reinforce a broken part and limp home.
Carry some mechanics wire.
Some sand or emery paper.
A spray can of degreaser.
Spare fuses, electrical wire, electrical connectors. and test light.
Some BARS Stop Leak if you have a coolant leak. That stuff works great, and have a gallon of water as well. You can use duct tape too to repair coolant hose, but leave the cap loose so it doesn't build up any pressure in the cooling system. You just have to remember to keep an eye on your engine temp, and if it starts pushing 205 or so, you should stop so it doesn't boil over.
That's the only reason you have a pressurize cooling system, is to raise the boiling point of the coolant. For every pound of pressure your cap is, you raise the boiling point three degrees. So, a 15 pound cap raises the boiling point 45 degrees. Now you go from 212 to 257 degrees before it boils over. That's why you never remove the cap when hot, because once the pressure is released, you instantly lower the boiling point back down to 212 and hot coolant comes boiling out FAST.
Sometimes you can use a piece of bike inner tube on top of the duct tape, and hose clamps to stop a coolant leak, and put the cap back on tight, but 15 psi is a lot of pressure and it might leak a little anyway.
A spare fan belt or one of those emergency fan belts that fits everything, and you cut it to fit the vehicle in need.
The last thing is a stick of Oyltite. That stuff will repair a leaking fuel tank, oil pan, transmission pan, and you don't have to drain the fuel or oil to repair them. This stuff works great and would have saved the Titanic.....I think.
For fast temporary repair on small engine leaks, use Oyltite-Stik. It stops oil and gasoline leaks without the need for equipment draining. Use Oyltite-Stik on low-pressure gas tanks, oil tanks, and more SDS Download 11475
markal.com
Also carry rags or something to clean yourself up, because nothing sucks worse than fixing a break down, and have to grab your steering wheel with filthy hands. I like to have some sort of eye protection too, to keep crap from falling into my eyes if I'm under a vehicle.
And BUG SPRAY. It sucks to have a break down, but it's worse when you're being eaten alive while trying to get back on the road.