Create session (Authentication request)

POST /api/v1/session

The merchant sends an authentication request and, on a successful response, receives a redirect_url — the link to the Checkout page. The session expires in 1 hour (configurable).

info

One link corresponds to a single payment. The link is invalidated after a successful payment.

Common parameters (all operations)

Parameter	Type	Required	Description
merchant_key	string	Yes	Merchant identification key
operation	string	Yes	purchase
methods	array	No	Payment methods allowed on the page. Optional — if omitted, pre-routing rules apply
order	object	Yes	Order details (see below)
cancel_url	string	No	Return URL if the payment is cancelled/declined
success_url	string	Yes	Return URL after a successful payment (max 1024)
error_url	string	No	Return URL on a Checkout technical error
customer	object	Conditional	Customer details
billing_address	object	Conditional	Billing address — top-level object, not nested inside customer
recurring_init	boolean	No	Initializes a recurring transaction
req_token	boolean	No	Requests card tokenization
hash	string	Yes	Special signature used to validate your request to the Payments Platform. See the Signature section. Must be the SHA1 of the MD5-encoded string (uppercased): recurring_init_trans_id + recurring_token + order.number + order.amount + order.description + merchant_pass

order object

Field	Type	Required	Description
number	string	Yes	Order ID in your system (max 255, recommended unique per attempt)
amount	string	Yes*	Amount. Check with S-interio, as each country has its own enabled amount limit
currency	string	Yes	ISO 4217. 3 chars for fiat, 3–6 chars for crypto
description	string	Yes	Product name (min 2, max 1024)

customer object

Field	Type	Description
name	string	Customer's full name. Must follow the first name + last name format, e.g. Juan Ramon Perez — no more than 3 fields (words) and no special characters
email	string	Email

billing_address object

Field	Type	Description
country	string	Country code, 2 letters (ISO 3166-1 alpha-2)
state	string	2 letters — fixed list only for USA, Canada, Australia, Japan, India
city	string	City
district	string	District/neighbourhood
address	string	Address
house_number	string	House number
zip	string	Postal code
phone	string	Customer's phone number
phone_country_code	string	Phone country code, e.g. +380

The billing_address object must look like this:

"billing_address": {
    "country": "MX",
    "state": "Ciudad de Mexico",
    "city": "Ciudad de Mexico",
    "address": "Av Arequipa 1234",
    "zip": "06000",
    "phone": "+524424667608"
}

warning

phone must include the country dialling code (e.g. +52 for Mexico).

Example request

View request

{
  "merchant_key": "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX",
  "operation": "purchase",
  "order": {
    "number": "1",
    "amount": "150000.00",
    "currency": "ARS",
    "description": "Purchase"
  },
  "cancel_url": "https://example.com/cancel",
  "success_url": "https://example.com/success",
  "error_url": "https://example.com/error",
  "customer": {
    "name": "Test Name",
    "email": "test-s-interio@example.com"
  },
  "billing_address": {
    "country": "AR",
    "state": "Cordoba",
    "city": "Cordoba",
    "address": "Av Arequipa 1234",
    "zip": "5000",
    "phone": "+5493482747561"
  },
  "recurring_init": true,
  "req_token": true,
  "hash": "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
}

Successful response

{
  "redirect_url": "{{CHECKOUT_HOST}/auth/ZXlKMGVYQWlPaUpLVjFRaUxDSmhiR2NpT2lKU1V6STFOaUo5..."
}

info

In the real response, redirect_url carries a long JWT/token as part of the path (/auth/{token}), not a short ID like abc123xyz. It is a signed token that Checkout generates and validates internally — you do not need to decode it, just redirect the customer to that full URL.

Customer return after payment

Once the payment is complete, the customer is redirected to the URL given in success_url or cancel_url.

About cancel_url

The return to cancel_url with parameters only happens if there was a decline and the payer closed the payment form (not the browser tab). If the payer closes the form without having pressed the PAY button, the redirect to cancel_url happens without additional parameters.

If a field is missing

If any request parameter is not sent and the payment method requires it, the field is shown directly on the Checkout Page for the customer to fill in.