A friction reduction tool and assembly are selectively activatable to produce fluid pressure pulses in downhole operations. The assembly includes a variable choke assembly having a rotary component and a stationary component, each with passages that enter into and out of alignment when the rotary component rotates with respect to the stationary component when driven by a rotor. The rotary component, stationary component, and rotor each have a central bore defining a central passage permitting fluid flow from above the assembly to below the assembly.