ISO 8583 Decline Explainer

How it works

POST /explain-decline

→

Validate input

→

Build audit trail

→

Explain response code

→

Return JSON + trail

Send a synthetic ISO 8583 authorization response and get back a plain-English explanation with an audit trail showing exactly which fields were used. Each explanation includes an uncertainty level (low/medium/high) based on how specific the response code is.

The service uses a public DE39 response code reference for rule-based explanations. All data is synthetic — no real cardholder or transaction data is used.

Try an example

DE39 = 05

Generic decline (Do not honor)

DE39 = 51

Insufficient funds

DE39 = 54

Expired card

DE39 = 43

Stolen card

DE39 = 55

Incorrect PIN

DE39 = 91

Issuer unavailable

Request POST

Ready

Response

Click "Send" or pick an example to see the explanation.

cURL examples

Copy and paste into your terminal.

curl -s -X POST /explain-decline \
  -H 'Content-Type: application/json' \
  -d '{
    "mti": "0110",
    "responseCode": "05",
    "amount": 127.50,
    "currency": "USD",
    "merchantCategory": "travel",
    "country": "AR",
    "syntheticCustomerContext": {
      "accountAgeDays": 400,
      "recentDeclines": 2,
      "riskLevel": "medium"
    }
  }'

curl -s -X POST /explain-decline \
  -H 'Content-Type: application/json' \
  -d '{
    "mti": "0210",
    "responseCode": "51",
    "amount": 500.00,
    "currency": "EUR",
    "merchantCategory": "retail",
    "country": "DE"
  }'