How to fill an air tank<br>Take your air tank to an air compressor. Full-service gas stations or truck stops are the most common locations that have air compressors. You can use the same pump motorists use to inflate the tires on their vehicles.
An air compressor can fill a tire and an air tank.
The agent states "You can use the same pump motorists use to inflate the tires on their vehicles." Therefore the air compressor can fill the air tank as well as tires. I think the AI is confused based on the wording. 
( z1 possible :ARG1 ( z2 fill :ARG0 ( z3 compressor :mod ( z4 air ) ) :ARG1 ( z5 and :op ( z6 tire ) :op ( z7 tank :mod z4 ) ) ) )