As Banzai mentioned, it's worth carrying a tire patch kit and levers, because the replacement tube is huge and is currently sold out, and you can fix a front flat like any other bike (do fatty's inflate on a single bulb?). But... fixing a rear tire flat is a big job, took me nearly two hours the first time I did it and that was at home. Mind you, a good chunk of that time was going back and forth between the bike and the radpower video on laptop on how to un/remount the rear wheel. I can tell you that in the supplied toolkit, the *biggest* crescent wrench is key; everything else needed you likely already have, but on the derailleur/power connection side you will be making a lot of little 1/8th turns on the axle nut while flipping that crescent wrench back and forth to get just a little bit of extra angle. The other key bit on re-seating the rear wheel is an *adjustable* crescent wrench (out of your own toolbox). The number of tools I'd have to carry to fix a rear fat on a ride is a fair amount of weight and hassle, so I don't do it.
So I'm saying, my plan for a rear tire flat more than 3 miles from home is a pair of 20s and "Yo, Taxi!" with a big smile.
But if you're asking what you should be stocking up for in advance? Yes, a tube fix kit. you can get them for 3-5 bucks, which is cheaper than swapping in a $15 new tube, when available. Also get small black tie-wraps, sometimes you need to snip and replace when fixing a flat. A spoke wrench is also in order. I started checking my spokes at 800 miles, my eyes got a little big at some of the ones needing 2.5 complete rotations.
Finally, whatever lock (u-lock or chain) you already have, get a biggus lockus of the other type. I've twice at supermarkets come on assholes sizing up my radrover for theft as I exited the store; thieves carry tools for breaking one kind of lock or the other, but usually not both.
Don't take this as shade, 1782 miles on my bike so far and happy.
