curl --request POST \
  --url https://api.mijnklantportaal.nl/v1/agreements \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'name=Service contract' \
  --form 'signerName=John Doe' \
  --form 'signerSignatureData=data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...' \
  --form 'signers={
  "firstName": "Dirk Jan",
  "lastName": "Bakker",
  "email": "dj.bakker@domain.com",
  "shouldIdentify": true
}' \
  --form 'documents=<string>' \
  --form documents.items='@example-file'

import requests

url = "https://api.mijnklantportaal.nl/v1/agreements"

files = { "documents.items": ("example-file", open("example-file", "rb")) }
payload = {
    "name": "Service contract",
    "signerName": "John Doe",
    "signerSignatureData": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...",
    "signers": "{
  \"firstName\": \"Dirk Jan\",
  \"lastName\": \"Bakker\",
  \"email\": \"dj.bakker@domain.com\",
  \"shouldIdentify\": true
}",
    "documents": "<string>"
}
headers = {"Authorization": "Bearer <token>"}

response = requests.post(url, data=payload, files=files, headers=headers)

print(response.text)

const form = new FormData();
form.append('name', 'Service contract');
form.append('signerName', 'John Doe');
form.append('signerSignatureData', 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...');
form.append('signers', '{
  "firstName": "Dirk Jan",
  "lastName": "Bakker",
  "email": "dj.bakker@domain.com",
  "shouldIdentify": true
}');
form.append('documents', '<string>');
form.append('documents.items', '{
  "fileName": "example-file"
}');

const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

options.body = form;

fetch('https://api.mijnklantportaal.nl/v1/agreements', 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://api.mijnklantportaal.nl/v1/agreements",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"name\"\r\n\r\nService contract\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerName\"\r\n\r\nJohn Doe\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerSignatureData\"\r\n\r\ndata:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signers\"\r\n\r\n{\r\n  \"firstName\": \"Dirk Jan\",\r\n  \"lastName\": \"Bakker\",\r\n  \"email\": \"dj.bakker@domain.com\",\r\n  \"shouldIdentify\": true\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents.items\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n{\r\n  \"fileName\": \"example-file\"\r\n}\r\n-----011000010111000001101001--",
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: multipart/form-data"
  ],
]);

$response = curl_exec($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://api.mijnklantportaal.nl/v1/agreements"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"name\"\r\n\r\nService contract\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerName\"\r\n\r\nJohn Doe\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerSignatureData\"\r\n\r\ndata:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signers\"\r\n\r\n{\r\n  \"firstName\": \"Dirk Jan\",\r\n  \"lastName\": \"Bakker\",\r\n  \"email\": \"dj.bakker@domain.com\",\r\n  \"shouldIdentify\": true\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents.items\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n{\r\n  \"fileName\": \"example-file\"\r\n}\r\n-----011000010111000001101001--")

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

	req.Header.Add("Authorization", "Bearer <token>")

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

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

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.mijnklantportaal.nl/v1/agreements")
  .header("Authorization", "Bearer <token>")
  .body("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"name\"\r\n\r\nService contract\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerName\"\r\n\r\nJohn Doe\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerSignatureData\"\r\n\r\ndata:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signers\"\r\n\r\n{\r\n  \"firstName\": \"Dirk Jan\",\r\n  \"lastName\": \"Bakker\",\r\n  \"email\": \"dj.bakker@domain.com\",\r\n  \"shouldIdentify\": true\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents.items\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n{\r\n  \"fileName\": \"example-file\"\r\n}\r\n-----011000010111000001101001--")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.mijnklantportaal.nl/v1/agreements")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request.body = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"name\"\r\n\r\nService contract\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerName\"\r\n\r\nJohn Doe\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signerSignatureData\"\r\n\r\ndata:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"signers\"\r\n\r\n{\r\n  \"firstName\": \"Dirk Jan\",\r\n  \"lastName\": \"Bakker\",\r\n  \"email\": \"dj.bakker@domain.com\",\r\n  \"shouldIdentify\": true\r\n}\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents\"\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"documents.items\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n{\r\n  \"fileName\": \"example-file\"\r\n}\r\n-----011000010111000001101001--"

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

{
  "id": "agr_abc12346def678",
  "name": "Service contract",
  "status": "sent",
  "signerName": "John Doe",
  "signerSignature": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...",
  "signerSignatureHash": "PwZVOc2K5rqcpqljbM2xkzJub9FtmA307pvuoJXoiqHDuEyZB7NVqdKbb3SPXt1P",
  "signers": [
    {
      "id": "ags_abc12346def678",
      "firstName": "Dirk Jan",
      "lastName": "Bakker",
      "email": "dj.bakker@domain.com",
      "shouldIdentify": true,
      "signature": "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAA...",
      "signatureHash": "PwZVOc2K5rqcpqljbM2xkzJub9FtmA307pvuoJXoiqHDuEyZB7NVqdKbb3SPXt1P",
      "signedAt": "2025-09-13T17:23:14+02:00"
    }
  ],
  "documents": [
    {
      "id": "agd_abc12346def678",
      "documentName": "Contract version_2.pdf",
      "fileSize": 512,
      "fileHash": "PwZVOc2K5rqcpqljbM2xkzJub9FtmA307pvuoJXoiqHDuEyZB7NVqdKbb3SPXt1P"
    }
  ],
  "createdAt": "2025-09-13T17:23:14+02:00"
}

{
  "message": "<string>"
}

{
  "message": "<string>"
}

{
  "message": "<string>"
}