curl --request POST \
  --url https://api.lemlist.com/api/contacts/lists/{listId}/entities \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "contactIds": [
    "ctc_abc123def456ghi78",
    "ctc_xyz789uvw012rst34"
  ]
}
'

import requests

url = "https://api.lemlist.com/api/contacts/lists/{listId}/entities"

payload = { "contactIds": ["ctc_abc123def456ghi78", "ctc_xyz789uvw012rst34"] }
headers = {
    "Authorization": "Basic <encoded-value>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Basic <encoded-value>', 'Content-Type': 'application/json'},
  body: JSON.stringify({contactIds: ['ctc_abc123def456ghi78', 'ctc_xyz789uvw012rst34']})
};

fetch('https://api.lemlist.com/api/contacts/lists/{listId}/entities', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

require 'uri'
require 'net/http'

url = URI("https://api.lemlist.com/api/contacts/lists/{listId}/entities")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Basic <encoded-value>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"contactIds\": [\n    \"ctc_abc123def456ghi78\",\n    \"ctc_xyz789uvw012rst34\"\n  ]\n}"

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

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.lemlist.com/api/contacts/lists/{listId}/entities",
  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([
    'contactIds' => [
        'ctc_abc123def456ghi78',
        'ctc_xyz789uvw012rst34'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Basic <encoded-value>",
    "Content-Type: application/json"
  ],
]);

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

curl_close($curl);

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

{
  "message": "Contacts added to list successfully",
  "addedCount": 2
}

"contactIds is required and must be a non-empty array"

"The authentication you supplied is incorrect"

"Contact list not found"