I never leave on a ride without a bike tool (basic set of allan wrenches and a screw driver), even when just riding the trails around the house. In fact, I keep one with every bike.
When I go out on the road, away from the house, I'll carry an inner tube with tire wrenches in a seat bag and then add a small portable hand pump in a handlebar bag. You should at least know how to repair a flat on your own. No one likes the job. Even if you decide you don't want to tackle the job, and decide to wait for someone to stop and help (bicyclists are very good about this), you'll have the inner tube and tools. Some folks forgo the inner tube and use a tube patch kit to save weight, but I've found that the inner tube with some flats is beyond repair or, the other extreme, as with a pinch flat, almost impossible to see where the tube is leaking.
For extreme backcountry expedition riding, some folks carry a chain tool with a repair chain link, but I've so rarely had a chain break, I don't bother. Doubt it's something you'd ever need.
As for any road riding, I always use a blinkie - a blinking red rear light - even during the day, no matter what. You just can't be too visible when sharing the road with vehicles. In a high traffic area, I'd use a front light, too, but we don't have that kind of traffic, up here. Lights are not a tool, of course, but I won't ride out on the road without one, anymore.