diff --git a/lib/API/MP/v1/API.php b/lib/API/MP/v1/API.php
index b726ffd727..7fa70ef0cb 100644
--- a/lib/API/MP/v1/API.php
+++ b/lib/API/MP/v1/API.php
@@ -1,7 +1,35 @@
 <?php
 namespace MailPoet\API\MP\v1;
 
+use MailPoet\Models\CustomField;
+
 if(!defined('ABSPATH')) exit;
 
 class API {
+  function getSubscriberFields() {
+    $data = array(
+      array(
+        'id' => 'email',
+        'name' => __('Email', 'mailpoet')
+      ),
+      array(
+        'id' => 'first_name',
+        'name' => __('First name', 'mailpoet')
+      ),
+      array(
+        'id' => 'last_name',
+        'name' => __('Last name', 'mailpoet')
+      )
+    );
+
+    $custom_fields = CustomField::selectMany(array('id', 'name'))->findMany();
+    foreach($custom_fields as $custom_field) {
+      $data[] = array(
+        'id' => 'cf_' . $custom_field->id,
+        'name' => $custom_field->name
+      );
+    }
+
+    return $data;
+  }
 }
\ No newline at end of file
diff --git a/lib/Models/CustomField.php b/lib/Models/CustomField.php
index b84d80e018..91acc36c26 100644
--- a/lib/Models/CustomField.php
+++ b/lib/Models/CustomField.php
@@ -7,6 +7,12 @@ if(!defined('ABSPATH')) exit;
 
 class CustomField extends Model {
   public static $_table = MP_CUSTOM_FIELDS_TABLE;
+  const TYPE_DATE = 'date';
+  const TYPE_TEXT = 'text';
+  const TYPE_TEXTAREA = 'textarea';
+  const TYPE_RADIO = 'radio';
+  const TYPE_CHECKBOX = 'checkbox';
+  const TYPE_SELECT = 'select';
 
   function __construct() {
     parent::__construct();
@@ -43,7 +49,7 @@ class CustomField extends Model {
 
   function formatValue($value = null) {
     // format custom field data depending on type
-    if(is_array($value) && $this->type === 'date' ) {
+    if(is_array($value) && $this->type === self::TYPE_DATE) {
       $custom_field_data = $this->asArray();
       $date_format = $custom_field_data['params']['date_format'];
       $date_type = (isset($custom_field_data['params']['date_type'])
diff --git a/tests/unit/Models/CustomFieldTest.php b/tests/unit/Models/CustomFieldTest.php
index d9eb649520..7e8387949f 100644
--- a/tests/unit/Models/CustomFieldTest.php
+++ b/tests/unit/Models/CustomFieldTest.php
@@ -8,7 +8,7 @@ class CustomFieldTest extends MailPoetTest {
   function _before() {
     $this->data = array(
       'name' => 'City',
-      'type' => 'text',
+      'type' => CustomField::TYPE_TEXT,
       'params' => array(
         'label' => 'What is your city?'
       )