Once you are planning a ski tour of several days, you should ask yourself: “What to take?” Who does not know the feeling of missing an important tool for your journey? Even if it a mere piece of tape to fix the skin to the ski, which could eventually save your whole tour.
Functional underwear, spare clothes, fleece jacket of sweater, ski touring pants and socks, wind- and waterproof jacket, thin as well as thick gloves (for the mount and descent respectively), warm hat, sun protection, touring shoes.
Touring ski, climbing skin (one spare pair per three tourers), adjustable poles, crampons, backpack, sunglasses, helmet, ski glasses, sunscreen, food, drinks (roughly 1 ½ litres), mobile phone (charged), map, altimeter, compass, maybe GPS, glue spray or tape for loose skins, headlamp, toiletries for multi-day tours.
Additions for alpine tours (high altitude):
Rope (at least 40 m), ice pick, crampons, chest and sit harness, two ordinary carbines, two screw-locker carabines, ice screws, mountaineer glasses, long slings, prusiks, accessory cord (5m).
LVS device (set to send), avalanche shovel, avalanche probe, first aid kit with survival blanket, bivouac sack, possibly ABS Avalanche Airbag System and AvaLung.