Air carrier flight crew reported an improperly worded cpdlc reroute from ATC on an oceanic flight.

Attributes
ACN	1482248
Time
Date	201709
Local Time Of Day	0601-1200
Place
Locale Reference	KZAK.ARTCC
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Widebody Transport
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Person 1
Function	Relief Pilot Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 12468 Flight Crew Type 9464
Person 2
Function	Relief Pilot Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 10693 Flight Crew Type 3522
Events
Anomaly	ATC Issue All Types Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types

Narrative:

We just crossed 45n40 on our oceanic clearance FL380. The next waypoints on our current clearance is 41n30; fatmo and amakr. At xa:13; we received a cpdlc reroute message from sfo:/clearedroute clearancearrival:BDEGA2.amakramakrwe printed the message and selected the load prompt on the FMC. We compared the printed message with the FMC; but failed to notice that 41n30 and fatmo were deleted. Upon accepting the message and executing the FMC; the aircraft immediately turned direct to amakr. After a short discussion with the other pilot we heading selected back to the original course towards 41n30; then rebuilt our FMC legs page to 41n30 fatmo amakr BDEGA2 arrival. We called sfo arinc on HF to clarify our clearance; arinc said they would ask sfo center. No immediate response then from arinc.at xa:20; we received a cpdlc message from sfo:/descend to reach FL370 by xa:25/report level FL370/for traffic. I needed you direct amakrwe printed; accepted and complied with this message:at xa:26; we sent a cpdlc message back to sfo:/your route clearance was ambiguous. Did not say direct amakr. Only specified arrival-BDEGA2.amak (could not complete our message due to character limitations for the cpdlc free text).

Original NASA ASRS Text

Title: Air carrier flight crew reported an improperly worded CPDLC reroute from ATC on an oceanic flight.

Narrative: We just crossed 45N40 on our oceanic clearance FL380. The next waypoints on our current clearance is 41N30; FATMO and AMAKR. At XA:13; we received a CPDLC reroute message from SFO:/CLEAREDROUTE CLEARANCEARRIVAL:BDEGA2.AMAKRAMAKRWe printed the message and selected the load prompt on the FMC. We compared the printed message with the FMC; but failed to notice that 41N30 and FATMO were deleted. Upon accepting the message and executing the FMC; the aircraft immediately turned direct to AMAKR. After a short discussion with the other pilot we heading selected back to the original course towards 41N30; then rebuilt our FMC Legs Page to 41N30 FATMO AMAKR BDEGA2 arrival. We called SFO ARINC on HF to clarify our clearance; ARINC said they would ask SFO Center. No immediate response then from ARINC.At XA:20; we received a CPDLC message from SFO:/DESCEND TO REACH FL370 BY XA:25/REPORT LEVEL FL370/FOR TRAFFIC. I NEEDED YOU DIRECT AMAKRWe printed; accepted and complied with this message:At XA:26; we sent a CPDLC message back to SFO:/YOUR RTE CLEARANCE WAS AMBIGUOUS. DID NOT SAY DIRECT AMAKR. ONLY SPECIFIED ARRIVAL-BDEGA2.AMAK (could not complete our message due to character limitations for the CPDLC free text).

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.