Tools required for trailbuilding? Shovel,
Saw,
Roulette (very long, perhaps even geodetic roulette),
Ax.


The trail will be built in a forest. So there's no rocks, just dirt, small stones and a lot of roots. What else will I need to build a good forest trail?
It depends a lot on the ambition of the trail and the local conditions. Are you trimming branches in a forest or creating a safe path down a rock face?

Other dirt-working tools will probably be helpful, a pick and wheelbarrow are the obvious ones I can think of. Knowlege of how to safely prune trees and plants, plus some knowlege of trail construction, and some skill at dealing with people might be handy (I'm not sure whether skills count as tools in the same way knowlege does).

Consumables like tree repair paint and gravel will be useful and possibly necessary.

If you have significant embankments you can definitely move concrete embankment bracing segments by hand, but a motor vehicle would make that easier. If you're using concrete a trowel would be good. If you're driving stakes a sledgehammer is essential (and if you're not, what holds your anti-erosion material in place?)

The limited MTB trail making I have done has all just required a spade, hammer and supply of pegs (I have used a small axe for the latter two but it's not a good idea). Stuff that I could carry on my bike, in other words.