It's not always so easy to get a ride or a taxi, especially if you're out in the woods. It can be a long walk. It always works out, but having equipment to cope with minor errors is a good idea.
Good to have with you:
Hose(s), pump/Co2, extra chain lock, chain breaker/Multitool, team patches (Park tool GP-2 kit and patches of glue sandpaper from Parktool VP-1), extra gear lug, some cable ties, With that kit you can do most things. I also have some Gorillatape that I wrap around the CO2 cartridge. A file for tires is good to have, so if the hole in the tire needs to be repaired, you can file it up. I also have a tool to be able to open a chain that has QL, mine is part of a larger kit, but there are several options.
Komplettera gärna med ett verktyg för att plugga ett däck, om du kör TL (tubeless). Stans DART är bäst. Park Tool TB-2C Tire Boot, för laga däck. En extra skruv till SPD pedal är också bra att ha, helst en hel SPD kloss, 2.5mm HEX för pedal och en Torx, bra öppna utsliten skurv. Tubolito är grymma extra slangar, kör du dem, tänk på att ta med laglappar för Tubolito, vanliga fungerar inte. En bit kedja och TVÅ quick-links, kan lösa problem med trasig kedja. En extra ventilkärna och verktyg för dessa, alltså ett ventilkärneverktyg. Bäst är Stan’s.
Fluid and energy in some form, and please plan (at least) a snack along the way. It splits the tour and is very nice. It is a good idea to bring reinforcements, especially in spring and autumn or if you are climbing at higher altitudes (a rule of thumb is that it gets about 1 degree colder per 200m of altitude). A warmer hat and a rain/windproof jacket are golden if there is a shower or headwinds.
Medkit in some form, good to have antihistamine, and alvedon and ipren. Takes no place, in Tuscany we cycled into a wasp nest, it can happen anywhere, antihistamine, is gold. Painkillers can help someone who is in pain. Better that the medkit is included than that it is too big. Plasters, bandages, some kind of antiseptic, e.g. you can go a long way with this canvas.