diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index f17db0a..9370a2a 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -2044,7 +2044,7 @@ function drupal_hash_base64($data) {
 /**
  * Generates a default anonymous $user object.
  *
- * @return Drupal\Core\Session\UserSessionInterface
+ * @return \Drupal\Core\Session\UserSessionInterface
  *   The user session object.
  */
 function drupal_anonymous_user() {
diff --git a/core/lib/Drupal/Core/Entity/EntityAccessController.php b/core/lib/Drupal/Core/Entity/EntityAccessController.php
index b82167a..0f9acc6 100644
--- a/core/lib/Drupal/Core/Entity/EntityAccessController.php
+++ b/core/lib/Drupal/Core/Entity/EntityAccessController.php
@@ -8,7 +8,6 @@
 namespace Drupal\Core\Entity;
 
 use Drupal\Core\Session\UserSessionInterface;
-use Drupal\user\Plugin\Core\Entity\User;
 
 /**
  * Defines a default implementation for entity access controllers.
@@ -82,8 +81,8 @@ public function deleteAccess(EntityInterface $entity, $langcode = LANGUAGE_DEFAU
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool|null
    *   TRUE if access was granted, FALSE if access was denied and NULL if access
diff --git a/core/lib/Drupal/Core/Entity/EntityAccessControllerInterface.php b/core/lib/Drupal/Core/Entity/EntityAccessControllerInterface.php
index 7ff9f83..11da8c9 100644
--- a/core/lib/Drupal/Core/Entity/EntityAccessControllerInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityAccessControllerInterface.php
@@ -23,8 +23,8 @@
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool
    *   TRUE if access was granted, FALSE otherwise.
@@ -40,8 +40,8 @@ public function viewAccess(EntityInterface $entity, $langcode = LANGUAGE_DEFAULT
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool
    *   TRUE if access was granted, FALSE otherwise.
@@ -57,8 +57,8 @@ public function createAccess(EntityInterface $entity, $langcode = LANGUAGE_DEFAU
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool
    *   TRUE if access was granted, FALSE otherwise.
@@ -74,8 +74,8 @@ public function updateAccess(EntityInterface $entity, $langcode = LANGUAGE_DEFAU
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool
    *   TRUE if access was granted, FALSE otherwise.
diff --git a/core/lib/Drupal/Core/Session/UserSession.php b/core/lib/Drupal/Core/Session/UserSession.php
index 5c50ccd..3ed8247 100644
--- a/core/lib/Drupal/Core/Session/UserSession.php
+++ b/core/lib/Drupal/Core/Session/UserSession.php
@@ -7,40 +7,109 @@
 
 namespace Drupal\Core\Session;
 
+/**
+ * An implementation of the user session interface for the global user.
+ *
+ * @todo: Change all properties to protected.
+ */
 class UserSession implements UserSessionInterface {
 
-  // @todo: Make these protected.
+  /**
+   * User ID.
+   *
+   * @var int
+   */
   public $uid;
+
+  /**
+   * Session hostname.
+   *
+   * @todo: This does not seem to be used, remove?
+   *
+   * @var string
+   */
   public $hostname;
+
+  /**
+   * List of the roles this user has.
+   *
+   * @var array
+   */
   public $roles;
+
+  /**
+   * Session ID.
+   *
+   * @var string.
+   */
   public $sid;
+
+  /**
+   * Secure session ID.
+   *
+   * @var string.
+   */
   public $ssid;
+
+  /**
+   * Session data.
+   *
+   * @var array.
+   */
   public $session;
+
+  /**
+   * .
+   *
+   * @var string.
+   */
   public $timestamp;
 
+  /**
+   * Constructs a new user session.
+   *
+   * @param array $values
+   *   Array of initial values for the user sesion.
+   */
   public function __construct(array $values = array()) {
     foreach ($values as $key => $value) {
       $this->$key = $value;
     }
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::id().
+   */
   public function id() {
     return $this->uid;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getRoles().
+   */
   public function getRoles() {
     return $this->roles;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSecureSessionId().
+   */
   public function getSecureSessionId() {
     return $this->ssid;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSessionData().
+   */
   public function getSessionData() {
     return $this->session;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSessionId().
+   */
   public function getSessionId() {
     return $this->sid;
   }
+
 }
\ No newline at end of file
diff --git a/core/lib/Drupal/Core/Session/UserSessionInterface.php b/core/lib/Drupal/Core/Session/UserSessionInterface.php
index 8dbd7a7..2e7cac7 100644
--- a/core/lib/Drupal/Core/Session/UserSessionInterface.php
+++ b/core/lib/Drupal/Core/Session/UserSessionInterface.php
@@ -7,10 +7,50 @@
 
 namespace Drupal\Core\Session;
 
+/**
+ * A user session object.
+ *
+ * Defines an object that has a user id, roles and can have session data. The
+ * interface is implemented both by the global session and the user entity.
+ */
 interface UserSessionInterface {
+  /**
+   * Returns the user ID or 0 for anonymous.
+   *
+   * @return int
+   *   The user ID.
+   */
   public function id();
+
+  /**
+   * Returns a list of roles.
+   *
+   * @return array
+   *   List of role IDs.
+   */
   public function getRoles();
+
+  /**
+   * Returns the session ID.
+   *
+   * @return string|NULL
+   *   The session ID or NULL if this user does not have an active session.
+   */
   public function getSessionId();
+
+  /**
+   * Returns the secure session ID.
+   *
+   * @return string|NULL
+   *   The session ID or NULL if this user does not have an active secure session.
+   */
   public function getSecureSessionId();
+
+  /**
+   * Returns the session data.
+   *
+   * @return array
+   *   Array with the session data that belongs to this object.
+   */
   public function getSessionData();
 }
\ No newline at end of file
diff --git a/core/modules/node/lib/Drupal/node/NodeAccessController.php b/core/modules/node/lib/Drupal/node/NodeAccessController.php
index c062538..06f8438 100644
--- a/core/modules/node/lib/Drupal/node/NodeAccessController.php
+++ b/core/modules/node/lib/Drupal/node/NodeAccessController.php
@@ -91,8 +91,8 @@ protected function access(EntityInterface $node, $operation, $langcode = LANGUAG
    *   (optional) The language code for which to check access. Defaults to
    *   LANGUAGE_DEFAULT.
    * @param \Drupal\Core\Session\UserSessionInterface $account
-   *   (optional) The user for which to check access, or NULL to check access
-   *   for the current user. Defaults to NULL.
+   *   (optional) The user session for which to check access, or NULL to check
+   *   access for the current user. Defaults to NULL.
    *
    * @return bool|null
    *   TRUE if access was granted, FALSE if access was denied or NULL if no
diff --git a/core/modules/user/lib/Drupal/user/Plugin/Core/Entity/User.php b/core/modules/user/lib/Drupal/user/Plugin/Core/Entity/User.php
index efcb8c8..dc71a88 100644
--- a/core/modules/user/lib/Drupal/user/Plugin/Core/Entity/User.php
+++ b/core/modules/user/lib/Drupal/user/Plugin/Core/Entity/User.php
@@ -176,18 +176,30 @@ public function id() {
     return $this->uid;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getRoles().
+   */
   public function getRoles() {
     return $this->roles;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSecureSessionId().
+   */
   public function getSecureSessionId() {
     return NULL;
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSessionData().
+   */
   public function getSessionData() {
     return array();
   }
 
+  /**
+   * Implements \Drupal\Core\Session\UserSessionInterface::getSessionId().
+   */
   public function getSessionId() {
     return NULL;
   }