Small Transport
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
ATC Issue All Types; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Human Factors
[We were] originally cleared to SJC via FMG HYP5 at 16;000 feet.While enroute to ELCAP at 16;000 feet Oakland Center [cleared] us 'Direct STUBL for the RAZRR2 arrival' with no additional altitude directions. We were then handed off to NorCal Approach. NorCal issued 'Direct RAZRR RAZRR2 Arrival.'We crossed RAZRR at 16;000 feet (6;000 feet below the publish altitude on the arrival). As we were making the turn over RAZRR; NorCal asked; 'Are you established on the RAZRR2?' We advised; 'Yes; we are making the turn over RAZRR now; do you show something else?' NorCal's reply was; 'No; it just looked like you weren't going to make the turn.'As we approached TRCOT; NorCal gave us a traffic advisory for an aircraft at 8;000 feet. We advised them; 'We are still at 16;000 feet; do you want lower?'NorCal replied; 'I asked if you were established on the RAZRR2; and you said 'yes' that means you are supposed to be descending according to the arrival.'We advised we had not been given 'Descend Via' at any point. We were then cleared to 6;500 feet and quickly descended there with no further incident.Use of the standard phraseology such as; 'Direct RAZRR for the RAZRR2; cross OUCHH at 16;000 then descend via the arrival' would have avoided the confusion.Also; if entering an arrival at such a low altitude; leaving the aircraft on an arrival without published crossing restrictions (such as the HYP5 we were originally cleared).
A Captain reported they were not aware that ATC expected them to 'descend via' the RAZRR2 arrival into SJC.