Those long, skinny wasps building little mud tubes on the side of your house are among the least dangerous wasps you'll find.
Mud daubers are solitary. No colony, no swarm, and no communal nest to defend. That alone removes the main reason social wasps become aggressive.
A female mud dauber simply builds mud cells and stocks them with food for her young. She hunts spiders, stings and paralyzes them, and seals them inside each chamber as a food supply for developing larvae.
Some species, including the blue mud dauber, are known to target black widows and other web-building spiders. In many cases they locate prey near webs or inside retreats rather than through coordinated 'hunting strategies.'
Mud daubers are very unlikely to sting unless physically handled or trapped. Their venom is adapted for subduing spider prey, not for defending a colony.
So that mud nest on your wall is usually a sign of a quiet, solitary hunter doing pest control on some of the more notorious spiders around your home.