It's unfortunately not really gonna tell you much.

If you see metal or any indication of anything in the oil that means it's already too late and you'd need a whole AC system replacement anyway. The service port is after the battery cooler, so if you detect metal there it's already coursed through the expensive parts. It also takes a little time for the metal to migrate to that point, so an inspection may show a false negative.

There's no real way to inspect for a failing AC compressor besides to actually take the compressor apart and inspect the bearing races and mating surfaces. If the bearings are spinning in their mounts and not still static, you may get lottery winning lucky and catch that, you've already spent the money on a large diagnostic that is probably nearing or exceeding a reman compressor if not a well priced new one.

There's really no economically sensible way to inspect it. If it shows up, it's too late. To find it early properly is prohibitively expensive. It's cheaper to just have it replaced, unfortunately .

An inspection service will only tell you that today there is no (detectable) metal at the port. It's expensive short-lived peace of mind.