The multi_token parameter is available on TRC-20 and all supported EVM-based blockchains, such as ERC-20, BEP-20, Polygon, Base and Arbitrum. It's optional, so you don't need to set it when making a request. Its default value is 0.
This parameter lets the same address_in receive payments in any token our system supports.
When you set this parameter, make sure your wallet address (address_out) supports the tokens you expect your customers to pay with. CryptAPI cannot reverse a payment in a token your wallet doesn't support.
It also means your customers can pay with any token our system supports, even tokens with very different prices. Your system should check the coin field and convert the price as needed. If you expect 1000 USDT (or equivalent) and your customer sends 1000 TRX, your system should be able to handle that.