How can i use VTEX payment API to make a purchase in my custom app

Integrations & API Payments
2

Hi there!

MAYBE there´re some fields missing.

Try to compare with this json
{

"paymentSystem": 4,
"paymentSystemName": "Mastercard",
"group": "creditCardPaymentGroup",
"installments": 1,
"installmentsValue": 699,
"value": 699,
"fields": {
    "holderName": "*****",
    "cardNumber": "***********03",
    "validationCode": "***",
    "dueDate": "*****",
    "addressId": "***************",
    "bin": "512269"
},
"transaction": {
    "id": "************",
    "merchantName": "*************"
},
"id": "*************",
"installmentValue": 699,
"currencyCode": "BRL"

}

EDIT: Try to check the steps described in this post.