Ask for the upfront price
Merchants may charge different prices by payment term or instrument and must display any discount, so compare the Pix or debit price with the installment price.
Check who is financing the installments
Sem juros installments are split by the merchant; com juros installments are credit from the issuer.
For com juros, get the CET and the total
The lender must tell you the CET, the effective monthly rate and the total to pay with and without financing before you accept.
Look at future obligations on your bill
Your bill shows the consolidated total of future installments and your available limit for each type of operation.