It seems odd to be considering building a bike from scratch if you don't know what tools would be involved. Most would be the same as for maintaining a bike, just as dedhed posted above.

In addition there are a lot of considerations of compatibility and suitability when choosing both a frame and the parts to go onto it.

Thirdly, it's generally a very poor financial decision to build a bike from scratch unless you are very familiar with the pro's and con's of the parts you are considering, both in general and how they apply to your body and riding style. Again, anyone who knows that much generally would not be asking questions about which tools to use.

Finally, the experience you gain from a full install is partially negated by the inevitable frustrations and the fact that the additional tasks are not ones you will do very often.

I have over 20 years of experience in repair and fitting of bikes, and when I was able to choose the "perfect" touring bike I opted for a Novara Randonneur but then changed out bars, stem, pedals, and saddle (and sold or transferred the parts to defray even those costs). I preferred to reserve the time a full assembly would have taken for riding and the money I would have spent on a custom install for spending in Italy.

Of course it's your choice if you want to build from scratch, but many do it for the wrong reasons.