Pay Engineers Pay Engineers API

API Reference

The Pay Engineers Compliance API is organized around REST. Our API has predictable resource-oriented URLs, accepts JSON request bodies, returns JSON-encoded responses, and uses standard HTTP response codes, authentication, and verbs.

You can use the API in sandbox without affecting live data. The API key you use to authenticate the request determines whether the request runs in sandbox or production.

Credentials are issued per compliance request and per environment, and published in your compliance portal once your request is validated.

API v1 — Baseline widely available

Local development — endpoints resolve to https://payengineers.com//api/v1

Just getting started?

Submit a compliance request to receive your sandbox credentials, then verify them with your first call.

Base URL

https://payengineers.com/api/v1

Tooling

Swagger UI openapi.json Postman

By default the examples use curl to interact with the API over HTTP. Import the OpenAPI spec to generate a client in your language.

Base URLs

Each environment has a dedicated API host. Use sandbox while building, staging for pre-production checks, and production only after your compliance request is validated and credentials are published.

EnvironmentVersioned API
Sandboxhttps://payengineers.com/api/v1
Staginghttps://payengineers.com/api/v1
Productionhttps://payengineers.com/api/v1

Environment hosts

Sandbox     https://payengineers.com/api
Staging     https://payengineers.com/api
Production  https://payengineers.com/api

Authentication

The API uses API keys to authenticate requests. You can view and manage your keys in the compliance portal once they are published for your request.

Sandbox keys start with pe_test_ and have unrestricted access to your sandbox. Send your key as an Authorization: Bearer header, and include your merchant identifier when available.

Your API keys carry many privileges — keep them secure. Do not share them in publicly accessible places such as GitHub or client-side code. Use GET /credentials/verify to confirm your key is active before going live.

Authenticated request

cURL 
curl https://payengineers.com/api/v1/credentials/verify \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY" \
  -H "X-Merchant-Id: $PAY_ENGINEERS_SANDBOX_MERCHANT_ID"
# The colon prevents curl from asking for a password.

Required headers

Authorization: Bearer <PAY_ENGINEERS_SANDBOX_API_KEY>
X-Merchant-Id: <PAY_ENGINEERS_SANDBOX_MERCHANT_ID>
Accept: application/json

Headers

Attributes

Authorization required
Required on protected routes. Bearer token from your published API key or access token.
X-Merchant-Id recommended
Must match the merchant identifier published for the same environment.
X-Pay-Engineers-Signature webhooks only
Present on inbound webhooks. Verify it using your webhook signing secret.

Example headers

GET /v1/merchant HTTP/1.1
Host: payengineers.com/api
Authorization: Bearer pe_test_51Tt17r...X400fxV8FBwU
X-Merchant-Id: pe_test_merchant_84fd
Accept: application/json

Errors

Pay Engineers uses conventional HTTP response codes to indicate the success or failure of an API request. Codes in the 2xx range indicate success, codes in the 4xx range indicate an error with the information provided, and codes in the 5xx range indicate a problem on our side.

Attributes

code string
A short string identifying the error programmatically, e.g. credential_expired.
message string
A human-readable message providing more details about the error.
errors nullable object
On validation errors, a map of field names to the failed rules.

HTTP status code summary

200OKEverything worked as expected.
401UnauthorizedNo valid API key provided, or credential expired.
403ForbiddenIP not allowlisted or merchant mismatch.
404Not FoundThe requested resource doesn't exist.
422ValidationInvalid request body on POST endpoints.
429Too Many RequestsRate limit hit — use exponential backoff.
5xxServer ErrorsSomething went wrong on our end. (These are rare.)

Error response

422 
{
  "code": "validation_error",
  "message": "The amount field is required.",
  "errors": {
    "amount": ["The amount field is required."]
  }
}

Health

Public liveness probe. No authentication required — use it for connectivity checks and uptime monitoring.

GET /health

Request

cURL 
curl -s "https://payengineers.com/api/v1/health"

Response

200 
{
  "status": "ok",
  "service": "pay-engineers-compliance-api",
  "version": "v1",
  "environment": "sandbox",
  "timestamp": "2026-07-16T12:00:00+00:00"
}

Credentials

Validates the bearer token and returns the merchant context, scopes and expiry. This is the ideal first call after copying credentials from the portal.

GET /credentials/verify

Request

cURL 
curl -s "https://payengineers.com/api/v1/credentials/verify" \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY" \
  -H "X-Merchant-Id: $PAY_ENGINEERS_SANDBOX_MERCHANT_ID"

Merchant

Returns the merchant identifier and processor context linked to the authenticated credential.

GET /merchant

Request

cURL 
curl -s "https://payengineers.com/api/v1/merchant" \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY" \
  -H "X-Merchant-Id: $PAY_ENGINEERS_SANDBOX_MERCHANT_ID"

Payments

List or create payments in the authenticated environment. Sandbox returns succeeded immediately for test flows.

GET /payments
POST /payments

Body parameters

amount integer, required
Amount in the smallest currency unit (e.g. cents).
currency string, required
Three-letter ISO currency code, e.g. EUR.
description string, optional
Free-text description shown in reports and receipts.

List payments

cURL 
curl -s "https://payengineers.com/api/v1/payments" \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY" \
  -H "X-Merchant-Id: $PAY_ENGINEERS_SANDBOX_MERCHANT_ID"

Create payment

cURL 
curl -s -X POST "https://payengineers.com/api/v1/payments" \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY" \
  -H "X-Merchant-Id: $PAY_ENGINEERS_SANDBOX_MERCHANT_ID" \
  -H "Content-Type: application/json" \
  -d '{"amount":1000,"currency":"EUR","description":"Test payment"}'

Webhooks

Returns a signed sample webhook payload so you can test signature verification before receiving live events.

POST /webhooks/sample

Replay protection (recommended)

  1. Read X-Pay-Engineers-Timestamp.
  2. Reject if older than 5 minutes.
  3. Compute the HMAC on timestamp + "." + raw_body.
  4. Compare using hash_equals().

Verification algorithm

PHP 
$expected = hash_hmac(
    'sha256',
    $rawRequestBody,
    getenv('PAY_ENGINEERS_SANDBOX_WEBHOOK_SECRET')
);
$valid = hash_equals($expected, $_SERVER['HTTP_X_PAY_ENGINEERS_SIGNATURE']);

Request a sample

cURL 
curl -s -X POST "https://payengineers.com/api/v1/webhooks/sample" \
  -H "Authorization: Bearer $PAY_ENGINEERS_SANDBOX_API_KEY"

API Explorer

Run real requests against sandbox from this page. Use a published sandbox key from your compliance request — no code required.

Response

Tip: for POST /payments, set the method to POST and keep the JSON body valid.

OpenAPI, Swagger and Postman

Use machine-readable specifications for CI pipelines, client generation and QA automation.

openapi.json

OpenAPI 3.0.3 source of truth.

Swagger UI

Try endpoints with auth in the browser.

Postman collection

Import and run environment tests.

Generate a client

shell 
# Example with openapi-generator
openapi-generator generate \
  -i https://payengineers.com/en/authorizations-compliance/docs/openapi.json \
  -g php \
  -o ./pay-engineers-client

Rate limits and retries

The default API rate limit is 60 requests per minute per API key or client IP. When you receive a 429, back off exponentially and keep the same reference / idempotency key when retrying POST /payments.

  • Exponential backoff: 1s, 2s, 4s, 8s.
  • Maximum 5 retries.
  • Never retry with a different idempotency key.

Rate limit headers

429 
Retry-After: 60
X-RateLimit-Limit: 60
X-RateLimit-Remaining: 12

Configuration

Store credentials in environment variables. Download a ready-made .env pack from your compliance request once parameters are published.

Available scopes

payments:read payments:write payouts:read payouts:write webhooks:manage webhooks:verify merchant:identify refunds:write

.env

dotenv 
PAY_ENGINEERS_SANDBOX_API_KEY=pe_test_...
PAY_ENGINEERS_SANDBOX_MERCHANT_ID=pe_test_...
PAY_ENGINEERS_SANDBOX_BASE_URL=https://payengineers.com/api
PAY_ENGINEERS_SANDBOX_API_URL=https://payengineers.com/api/v1
PAY_ENGINEERS_SANDBOX_WEBHOOK_SECRET=whsec_test_...
PAY_ENGINEERS_API_VERSION=v1

CDN & JavaScript SDK

Load the lightweight SDK from our CDN. In production it is served from cdn.payengineers.com.

CDN base: https://payengineers.com/cdn

Browser integration

HTML 
<script src="https://payengineers.com/cdn/compliance/v1/pay-engineers-sdk.js"></script>
<script>
  const client = PayEngineers.createClient({
    apiKey: '...',
    merchantId: '...',
    baseUrl: 'https://payengineers.com/api/v1',
    environment: 'sandbox',
  });
  client.health().then(console.log);
</script>

Examples

Copy-paste snippets for the most common stacks. Both examples list payments in sandbox using environment variables for credentials.

List payments

PHP 
$ch = curl_init('https://payengineers.com/api/v1/payments');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv('PAY_ENGINEERS_SANDBOX_API_KEY'),
        'X-Merchant-Id: ' . getenv('PAY_ENGINEERS_SANDBOX_MERCHANT_ID'),
        'Accept: application/json',
    ],
]);
echo curl_exec($ch);

List payments

Node.js 
const res = await fetch('https://payengineers.com/api/v1/payments', {
  headers: {
    Authorization: `Bearer ${process.env.PAY_ENGINEERS_SANDBOX_API_KEY}`,
    'X-Merchant-Id': process.env.PAY_ENGINEERS_SANDBOX_MERCHANT_ID,
    Accept: 'application/json',
  },
});
console.log(await res.json());

Changelog and versioning

v1.2.0 — 2026-07-16

Added OpenAPI and Postman exports, API Explorer and webhook replay guidance.

v1.1.0 — 2026-07-10

Introduced /webhooks/sample and the credential verify endpoint.

Versioning rules

  • Breaking changes are released only on new major versions.
  • v1 endpoints remain stable for at least 12 months after a deprecation notice.
  • Deprecation notices are published in the docs and in response headers.

Go-live checklist

Work through both lists before switching production traffic to your integration.

Pre-production

  • Sandbox pack published (API key, merchant ID, endpoint, webhook secret).
  • At least one connection test passed.
  • Webhook signature verification implemented.
  • Rate limit handling and retries tested.

Production launch

  • Switch to the production base URL and production credentials.
  • Restrict credentials using allowlisted IPs.
  • Enable monitoring on /health and critical flows.
  • Plan credential rotation every 90 days.

Language guides

Additional tutorials published by Pay Engineers.

php

PHP cURL quickstart

A minimal, dependency-free PHP example for calling a published sandbox endpoint with an API key, plus guidance on authentication headers, error handling, environment variables and secret rotation.

laravel

Laravel HTTP client guide

How to consume published compliance credentials from a Laravel application using the HTTP facade, including config binding, retry/backoff strategy, error handling and safe secret storage.

nodejs

Node.js fetch sample

A Node.js example using the native fetch API to authenticate against a sandbox endpoint, covering environment configuration, timeout handling, retries and safe logging of processor responses.

java

Java HttpClient sample

A Java 11+ example built on the standard library HttpClient, showing authentication, timeout configuration, response handling and where to store processor credentials in a typical Spring application.

python

Python requests sample

A Python example using the requests library to call a sandbox endpoint securely, with guidance on environment variables, session reuse, timeouts, retries and structured error handling.

dotnet

.NET HttpClient sample

A .NET example showing how to consume sandbox and production endpoints from ASP.NET or a console application, including dependency injection, typed clients, Polly retry policies and secret configuration.