diff --git a/src/OAuth2/Storage/SessionInterface.php b/src/OAuth2/Storage/SessionInterface.php
index 84651909..60c126ac 100644
--- a/src/OAuth2/Storage/SessionInterface.php
+++ b/src/OAuth2/Storage/SessionInterface.php
@@ -137,8 +137,8 @@ interface SessionInterface
      * )
      * </code>
      *
-     * @param  [type] $accessToken [description]
-     * @return [type]              [description]
+     * @param  string     $accessToken  The access token
+     * @return bool|array               Returns false if the validation fails, array on success
      */
     public function validateAccessToken($accessToken);
 
@@ -161,7 +161,7 @@ interface SessionInterface
      * Validate a refresh token
      * @param  string $refreshToken The refresh token
      * @param  string $clientId     The client ID
-     * @return int                  The session ID
+     * @return bool|int             The session ID, or false on failure
      */
     public function validateRefreshToken($refreshToken, $clientId);