A9S

I don't like this play at all.
With a short stacked limper already you need to decide first if your hand is strong enough to take him on if he shoves to your raise.
If you think it is, your raise needs to be bigger, so around 1000.
If not then its probably just a fold from MP. If you flat call you leave the possibility of someone squeezing after.
As played, I think call flop is ok, could put in a raise which is probably what I would do, that's just a personal preference of mine to donk bets on flop.
Turn again I might bet but check behind is ok to manage pot size.
River is a definite call for 1BB but probably knowing you are beat.
Its possible to consider a big raise on the river but villain could easily have played FD this way so not advisable

Hey Adam!

If you want to raise pre -> make 900 at least for a little fe!
You're giving also your opponents behind the chance to get into the pot!

As played its ok imo!
River is no raise... you still have sd-value! Why would you raise? A ten is never folding anyway on this limit!

greets,
Tiltberger