diff --git a/manualcrop.api.php b/manualcrop.api.php
new file mode 100644
index 0000000..5137874
--- /dev/null
+++ b/manualcrop.api.php
@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @file
+ * API documentation for Manual Crop
+ */
+
+/**
+ * Implements hook_manualcrop_supported_widgets_alter().
+ *
+ * Allow other modules to Manual Crop and extend supported widget types.
+ */
+function hook_manualcrop_supported_widgets_alter(&$widgets) {
+  // Widget name + optional settings.
+  $widgets['widget_name'] = array(
+    'thumbnails',
+  );
+}
diff --git a/manualcrop.helpers.inc b/manualcrop.helpers.inc
index 3a8166b..715bf60 100644
--- a/manualcrop.helpers.inc
+++ b/manualcrop.helpers.inc
@@ -30,6 +30,7 @@ function manualcrop_supported_widgets($widget_type = NULL, $settings = array())
     'image_miw' => $optional_settings,
     'media_generic' => array('thumblist'),
   );
+  drupal_alter('manualcrop_supported_widgets', $widgets);
 
   // Make sure $settings contains only valid entries.
   if (!empty($settings)) {