In the validateSinglePaymentUsing call what does the code: "AGT012",description:"Description not matching the provided restriction" error mean?

The code: ‘AGT012’,description:‘Description not matching the provided restriction’ error is returned if the bank (ASPSP) does not accept characters (e.g. special characters). In the SerchBanks call, the ‘unstrRemittanceRegexp’ field shows the restrictions for each individual bank.