pass (definition 3) noun
: a single passage or movement (as of an airplane) over a place or toward a target
pass (definition 1) noun - ODO
1 An act or instance of moving past or through something.
‘repeated passes with the swipe card’
1.5 Computing A single scan through a set of data or a program.
‘The whole thing can now be done with a single pass, using a single repository and that's a big boon.’
The metaphor comes from the idea of going past something multiple times to examine it, but referencing only the first pass.
For example, if you're piloting a rescue plane and looking for something in the water, you can't stop the plane in mid air near the location of interest, but you can fly past it several times. Naturally, your initial impressions are formed on the first pass.
The natural reading of your quote is that the author was unable to fully but succinctly explain what it means "to be a rational agent in a corresponding sense", but opted to communicate something useful and fairly representative about that notion nonetheless.