A shaped charge is the usual tool. Penetration, entrance-hole size, shot density in shots per foot, and the angle between shots are chosen for the gun and the rock. A tunnel crushed by the charge is a restriction until it is cleaned.
Shooting with the wellbore pressure below the pore pressure, or surging the tunnels afterwards, is done to push that crushed debris out. Perforations that do not connect to permeable rock, or that are plugged with charge debris and mud solids, show up as a high skin and a productivity index below what the reservoir would suggest.