My parents are visiting me with a B2 visa. They meet the substantial presence test. Is there any additional restriction for them to be tax resident in the US so I can claim them as dependants?
Thanks,

Yes, they meet citizen or resident test:
"A dependent must be a U.S. citizen, U.S. resident alien, U.S. national or a resident of Canada or Mexico, for some part of the year."

Now the other requirements are that you provided more than half of their support. The parent's worldwide income for the year must be less than $3500.