This is a collection of experience and incidents such as I can remember some of my misspent youth and thrash through my later years.
The beatings will continue until moral improves.
Tools and Spares on a Bicycle
When I built a new seat bag tool kit I had CO2, a questionable hand pump that had once been good, but at some point stopped working all that well. I was using latex tubes. The Swiss Army knife was there for the scissors and screwdrivers. The quick patches worked sometimes.

My current pack is below.

I don’t carry a chain breaker like I used to. That is down to there not being room in the seat pack I carry now. When I began searching for the above set I assembled I looked at all the multi tools and tool kit bundles and found none included all the wrenches I needed, in fact the specific Torx size for the Pinarello F7 seat pin and bars was not included in ANY set I looked at. That fact led me to build my own.
I got a Lezyne pack that has proved to be wanting a bit.

The biggest problem with he above bag is the velcro on the straps is not good enough to both connect the bag to the rails and hold the bag snug and secure. The velcro lets go when I use it without an extra strap. I had to add the strap and randomly had a spare that worked well enough. But, I’m not happy with that solution. The bag is a touch too small as well. For Winter I’ve changed to using the bottle cage tool holder.

This setup still doesn’t hold the chain breaker. I little bit of rearranging and I managed to include the chain breaker, but exclude the Swiss Army knife. The chain breaker has a small straight blade screw driver that may be enough for the kit. When I get my bicycle back from it’s crash repair, I’ll check to make sure it all works.

I managed to fit everything into the bag. One hex wrench could also be removed along with the knife. I do carry a smaller keychain Swiss Army knife in my jersey pocket.

And all packed up and on for weight,

As an example of these built up tool packs, the Topeak Elementa Garbage EX. This kit like every other kit I’ve checked is missing a T20 Torx bit. Which is what led me to buy hex and Torx wrenches from Feedback and use them in my seat bag. I like the Topeak bag and strap system, I’m not too interested in the tool kit. So, my search for the perfect bag continues. I plan a trip to REI eventually to look at bag straps. The strap I’m using is not terrible, but not precisely what I want. For now, it works and was free being cast off from some other bag that has come through my collection.