curl --request GET \
  --url https://your-instance.example.com/api/{session}/contacts/check \
  --header 'Authorization: Bearer <token>'

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

fetch('https://your-instance.example.com/api/{session}/contacts/check', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://your-instance.example.com/api/{session}/contacts/check"

headers = {"Authorization": "Bearer <token>"}

response = requests.get(url, headers=headers)

print(response.text)

package main

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

func main() {

	url := "https://your-instance.example.com/api/{session}/contacts/check"

	req, _ := http.NewRequest("GET", url, nil)

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

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

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

	fmt.Println(string(body))

}

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://your-instance.example.com/api/{session}/contacts/check",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>"
  ],
]);

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

curl_close($curl);

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

[
  {
    "exists": true,
    "lid": "<string>",
    "phoneNumber": "<string>"
  }
]

{
  "docs": "https://docs.polymorfa.com/api/messages/send",
  "error": "missing required field: chatId"
}

{
  "error": "missing or invalid API key"
}

{
  "error": "internal server error"
}

{
  "docs": "<string>",
  "error": "<string>"
}