curl --request POST \
  --url https://www.merchkit.com/api/v1/vendors/upsert \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "merge_key": "vendor_name",
  "attributes": {
    "vendor_name": "Nordic Timber Co.",
    "country": "Denmark"
  }
}
'

import requests

url = "https://www.merchkit.com/api/v1/vendors/upsert"

payload = {
    "merge_key": "vendor_name",
    "attributes": {
        "vendor_name": "Nordic Timber Co.",
        "country": "Denmark"
    }
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    merge_key: 'vendor_name',
    attributes: {vendor_name: 'Nordic Timber Co.', country: 'Denmark'}
  })
};

fetch('https://www.merchkit.com/api/v1/vendors/upsert', 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://www.merchkit.com/api/v1/vendors/upsert",
  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([
    'merge_key' => 'vendor_name',
    'attributes' => [
        'vendor_name' => 'Nordic Timber Co.',
        'country' => 'Denmark'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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://www.merchkit.com/api/v1/vendors/upsert"

	payload := strings.NewReader("{\n  \"merge_key\": \"vendor_name\",\n  \"attributes\": {\n    \"vendor_name\": \"Nordic Timber Co.\",\n    \"country\": \"Denmark\"\n  }\n}")

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

	req.Header.Add("Authorization", "Bearer <token>")
	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://www.merchkit.com/api/v1/vendors/upsert")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"merge_key\": \"vendor_name\",\n  \"attributes\": {\n    \"vendor_name\": \"Nordic Timber Co.\",\n    \"country\": \"Denmark\"\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.merchkit.com/api/v1/vendors/upsert")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"merge_key\": \"vendor_name\",\n  \"attributes\": {\n    \"vendor_name\": \"Nordic Timber Co.\",\n    \"country\": \"Denmark\"\n  }\n}"

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

{
  "data": {
    "id": "77e1b2aa-6b3d-4f19-9d10-8c2a5e7f4b21",
    "type": "vendor",
    "label": "Nordic Timber Co.",
    "parent_id": null,
    "created_at": "2026-06-02T14:11:09Z",
    "updated_at": "2026-07-18T09:30:22Z",
    "attributes": {
      "vendor_name": "Nordic Timber Co.",
      "website": "https://nordictimber.example",
      "country": "Denmark",
      "lead_time_days": 21
    }
  }
}

{
  "data": {
    "id": "77e1b2aa-6b3d-4f19-9d10-8c2a5e7f4b21",
    "type": "vendor",
    "label": "Nordic Timber Co.",
    "parent_id": null,
    "created_at": "2026-06-02T14:11:09Z",
    "updated_at": "2026-07-18T09:30:22Z",
    "attributes": {
      "vendor_name": "Nordic Timber Co.",
      "website": "https://nordictimber.example",
      "country": "Denmark",
      "lead_time_days": 21
    }
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "Unknown attribute key(s): colour.",
    "documentation_url": "https://docs.merchkit.com/developers/errors#validation_failed",
    "is_retriable": false,
    "retry_after_seconds": null,
    "alternative_action": "List valid attribute keys via GET /v1/attributes?type=product.",
    "request_id": "req_01j9x2k8",
    "field_errors": [
      {
        "field": "colour",
        "issue": "not_a_defined_attribute"
      }
    ]
  }
}

{
  "error": {
    "code": "validation_failed",
    "message": "Unknown attribute key(s): colour.",
    "documentation_url": "https://docs.merchkit.com/developers/errors#validation_failed",
    "is_retriable": false,
    "retry_after_seconds": null,
    "alternative_action": "List valid attribute keys via GET /v1/attributes?type=product.",
    "request_id": "req_01j9x2k8",
    "field_errors": [
      {
        "field": "colour",
        "issue": "not_a_defined_attribute"
      }
    ]
  }
}