You must provide a device_name, a description and an amount to process to payment

This is my code:

$params='device_name=miguelcel&description=ladescripcion&amount='.floatval($_POST["importe"]).'&cc_type=debit_card&external_reference='.$idFactura.'&disable_back_button=true&notification_url=https://www.nose.com&payer_email='.$_POST["correo"].';';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://mobile.mercadopago.com/point/services/integrations/v1?access_token=".$access_token."");
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json;'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, $params);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);

$respuesta = curl_exec($ch);
curl_close($ch);

Mark the following error:

  

{"message": "You must provide a device_name, a description and an amount to process to payment", "error": "bad_request", "status": 400, "cause": []}