curl --request POST \
  --url https://merchant-url.com/api/universal_api \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "event": "cart.addons",
  "data": {
    "addons_limit": 3
  }
}
'

import requests

url = "https://merchant-url.com/api/universal_api"

payload = {
    "event": "cart.addons",
    "data": { "addons_limit": 3 }
}
headers = {
    "X-API-Key": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'X-API-Key': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({event: 'cart.addons', data: {addons_limit: 3}})
};

fetch('https://merchant-url.com/api/universal_api', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://merchant-url.com/api/universal_api",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'event' => 'cart.addons',
    'data' => [
        'addons_limit' => 3
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-API-Key: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://merchant-url.com/api/universal_api"

	payload := strings.NewReader("{\n  \"event\": \"cart.addons\",\n  \"data\": {\n    \"addons_limit\": 3\n  }\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("X-API-Key", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://merchant-url.com/api/universal_api")
  .header("X-API-Key", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"event\": \"cart.addons\",\n  \"data\": {\n    \"addons_limit\": 3\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://merchant-url.com/api/universal_api")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["X-API-Key"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"event\": \"cart.addons\",\n  \"data\": {\n    \"addons_limit\": 3\n  }\n}"

response = http.request(request)
puts response.read_body

{
  "event": "cart.addons",
  "status": "success",
  "data": {
    "addons": [
      {
        "name": "Blue Hat",
        "description": " Large blue satin hat with initials embroidered.",
        "reference": "1123",
        "image_url": "https://boltswagstore.com/inventory/hats/red-hat.png",
        "amount": 15000,
        "currency": "USD",
        "product_page_url": "<string>"
      }
    ]
  }
}

{
  "event": "cart.addons",
  "status": "failure",
  "errors": [
    {
      "code": 2001005,
      "data": [
        {
          "reason": "This product is out of stock."
        }
      ]
    }
  ]
}