That would be the ultimate minimalist survival kit, wouldn't it?

"Brain?" "Check!"
"Multitool?" "Check!"

Mindset and improvisation would be your most critical tools. Just doing some thinking and comparing to some of the basic essentials. You might have to identify some helpful medicinal plants or improvise a bandage; build a shelter with natural materials; make a bow drill to create fire; use natural materials and charcoal from your fire to filter water; make a container from a section of a log to carry water and purify the water by using hot rocks to boil it; and improvise a snare or fishing items to get some food in your belly. What would it take to pull all this off? Knowledge, skill and practice. And something a little more intangible: the will to survive.

Why don't we normally advise taking such a minimalist approach? Well, just add something like a broken arm, dislocated shoulder, or other serious injury and suddenly improvising all your needs takes on a new and tortuous agony. Or so I've been told. Not been there and certainly don't want to do that.