diff --git a/CRM/Financial/BAO/PaymentProcessor.php b/CRM/Financial/BAO/PaymentProcessor.php
index 80125a8edc5c..0805e17cec03 100644
--- a/CRM/Financial/BAO/PaymentProcessor.php
+++ b/CRM/Financial/BAO/PaymentProcessor.php
@@ -402,6 +402,21 @@ public static function getPaymentProcessors($capabilities = array(), $ids = FALS
 
   /**
    * Is there a processor on this site with the specified capability.
+   *
+   * The capabilities are defined on CRM_Core_Payment and can be extended by
+   * processors.
+   *
+   * examples are
+   *  - supportsBackOffice
+   *  - supportsLiveMode
+   *  - supportsFutureRecurDate
+   *  - supportsCancelRecurring
+   *  - supportsRecurContributionsForPledges
+   *
+   * They are passed as array('BackOffice');
+   *
+   * Details of specific functions are in the docblocks on the CRM_Core_Payment class.
+   *
    * @param array $capabilities
    *
    * @return bool