diff --git a/classes/completionscanner.php b/classes/completionscanner.php
index 364426d..cecf519 100644
--- a/classes/completionscanner.php
+++ b/classes/completionscanner.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <https://www.gnu.org/licenses/>.
 /**
- *
+ * Scan course completion criteria for pending grading actions
  * @package    local_treestudyplan
  * @copyright  2023 P.M. Kuipers
  * @license    https://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
@@ -26,24 +26,56 @@ defined('MOODLE_INTERNAL') || die();
 require_once($CFG->libdir.'/externallib.php');
 
 use \grade_item;
+use \completion_criteria;
 
+/**
+ * Scan course completion criteria for pending grading actions
+ */
 class completionscanner {
+    /**
+     * Cache of supported mods
+     * @var array 
+     */
     private static $modsupported = [];
+    /**
+     * Cache of enrolled students in a particular course
+     * @var array
+     */
     private static $coursestudents = [];
+    /** The internally used grading scanner
+     * @var local\ungradedscanners\scanner_base
+     */
     private $scanner = null;
-    private $course = null;
+    /** 
+     * Course module
+     * @var \cm_info
+     */
     private $cm = null;
+    /** @var grade_item */
     private $gi = null;
+    /**
+     * Cache of pending ungraded results per user
+     * @var array
+     */
     private $pendingcache = [];
 
-    public static function supported($mod) {
+    /**
+     * Check if a certain activity type is supported for scanning pending results
+     * @param string $mod name of activity module
+     */
+    public static function supported($mod) : bool {
         if (!array_key_exists($mod, self::$modsupported)) {
             self::$modsupported[$mod] = class_exists("\local_treestudyplan\\local\\ungradedscanners\\{$mod}_scanner");
         }
         return self::$modsupported[$mod];
     }
 
-    public static function get_course_students($courseid) {
+    /** 
+     * List all users enrolled in a course as student by userid
+     * @param int $courseid Course id of the course to check
+     * @return int[] Array if user ids
+     */
+    public static function get_course_students($courseid) : array {
         global $CFG;
         if (!array_key_exists($courseid, self::$coursestudents)) {
             $students = [];
@@ -57,7 +89,12 @@ class completionscanner {
         return self::$coursestudents[$courseid];
     }
 
-    public function __construct(\completion_criteria $crit, $course) {
+    /**
+     * Construct new scanner based on completion criteria and course
+     * @param completion_criteria $crit Criteria to check for
+     * @param stdClass $course Course DB record
+     */
+    public function __construct(completion_criteria $crit, $course) {
         $this->courseid = $course->id;
         $this->course = $course;
         $this->modinfo = get_fast_modinfo($course);
@@ -91,18 +128,26 @@ class completionscanner {
 
     }
 
-    public function pending($userid) {
-        if (!array_key_exists($userid, $this->pending_cache)) {
+    /**
+     * Check if the criteria this scanner scans has pending submissions for a specific user
+     * @param int $userid ID of the user to check for
+     */
+    public function pending($userid) : bool {
+        if (!array_key_exists($userid, $this->pendingcache)) {
             if ($this->scanner === null) {
-                $this->pending_cache[$userid] = false;
+                $this->pendingcache[$userid] = false;
             } else {
-                $this->pending_cache[$userid] = $this->scanner->has_ungraded_submission($userid);;
+                $this->pendingcache[$userid] = $this->scanner->has_ungraded_submission($userid);;
             }
         }
-        return $this->pending_cache[$userid];
+        return $this->pendingcache[$userid];
     }
 
-    public static function structure($value = VALUE_OPTIONAL) {
+    /**
+     * Webservice structure for basic info
+     * @param int $value Webservice requirement constant
+     */
+    public static function structure($value = VALUE_OPTIONAL) : \external_description {
         return new \external_single_structure([
             "ungraded" => new \external_value(PARAM_INT, 'number of ungraded submissions'),
             "completed" => new \external_value(PARAM_INT, 'number of completed students'),
@@ -112,7 +157,10 @@ class completionscanner {
         ], "details about gradable submissions", $value);
     }
 
-    public function model() {
+    /**
+     * Webservice model for basic info
+     */
+    public function model() : array {
 
         // Get completion info.
         $students = self::get_course_students($this->courseid);
diff --git a/classes/gradingscanner.php b/classes/gradingscanner.php
index 500d3ac..11c703e 100644
--- a/classes/gradingscanner.php
+++ b/classes/gradingscanner.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <https://www.gnu.org/licenses/>.
 /**
- *
+ * Scan gradables for a pending grading action
  * @package    local_treestudyplan
  * @copyright  2023 P.M. Kuipers
  * @license    https://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
@@ -27,21 +27,49 @@ require_once($CFG->libdir.'/externallib.php');
 
 use \grade_item;
 
+/**
+ * Scan gradables for a pending grading action
+ */
 class gradingscanner {
+    /**
+     * Cache of supported mods
+     * @var array 
+     */
     private static $modsupported = [];
+    /**
+     * Cache of enrolled students in a particular course
+     * @var array
+     */
     private static $coursestudents = [];
+    /** The internally used grading scanner
+     * @var local\ungradedscanners\scanner_base
+     */
     private $scanner = null;
+    /** @var grade_item */
     private $gi = null;
+    /**
+     * Cache of pending ungraded results per user
+     * @var array
+     */
     private $pendingcache = [];
 
-    public static function supported($mod) {
+    /**
+     * Check if a certain activity type is supported for scanning pending results
+     * @param string $mod name of activity module
+     */
+    public static function supported($mod) : bool {
         if (!array_key_exists($mod, self::$modsupported)) {
             self::$modsupported[$mod] = class_exists("\local_treestudyplan\\local\\ungradedscanners\\{$mod}_scanner");
         }
         return self::$modsupported[$mod];
     }
 
-    public static function get_course_students($courseid) {
+    /** 
+     * List all users enrolled in a course as student by userid
+     * @param int $courseid Course id of the course to check
+     * @return int[] Array if user ids
+     */
+    public static function get_course_students($courseid) : array {
         global $CFG;
         if (!array_key_exists($courseid, self::$coursestudents)) {
             $students = [];
@@ -55,6 +83,10 @@ class gradingscanner {
         return self::$coursestudents[$courseid];
     }
 
+    /**
+     * Construct new scanner based on grade item
+     * @param grade_item $gi Grade item
+     */
     public function __construct(grade_item $gi) {
         $this->courseid = $gi->courseid;
         $this->gi = $gi;
@@ -64,22 +96,33 @@ class gradingscanner {
         }
     }
 
-    public function is_available() {
+    /** 
+     * Check if this scanner is usable (has an internal activity specific scanner)
+     */
+    public function is_available() : bool {
         return $this->scanner !== null;
     }
 
-    public function pending($userid) {
-        if (!array_key_exists($userid, $this->pending_cache)) {
+    /**
+     * Check if the gradable item this scanner scans has pending submissions for a specific user
+     * @param int $userid ID of the user to check for
+     */
+    public function pending($userid) : bool {
+        if (!array_key_exists($userid, $this->pendingcache)) {
             if ($this->scanner === null) {
-                $this->pending_cache[$userid] = false;
+                $this->pendingcache[$userid] = false;
             } else {
-                $this->pending_cache[$userid] = $this->scanner->has_ungraded_submission($userid);;
+                $this->pendingcache[$userid] = $this->scanner->has_ungraded_submission($userid);;
             }
         }
-        return $this->pending_cache[$userid];
+        return $this->pendingcache[$userid];
     }
 
-    public static function structure($value =VALUE_OPTIONAL) {
+    /**
+     * Webservice structure for basic info
+     * @param int $value Webservice requirement constant
+     */
+    public static function structure($value = VALUE_OPTIONAL) : \external_description {
         return new \external_single_structure([
             "ungraded" => new \external_value(PARAM_INT, 'number of ungraded submissions'),
             "completed" => new \external_value(PARAM_INT, 'number of completed students'),
@@ -89,7 +132,10 @@ class gradingscanner {
         ], "details about gradable submissions", $value);
     }
 
-    public function model() {
+    /**
+     * Webservice model for basic info
+     */
+    public function model() : array {
         // Upda.
         $students = self::get_course_students($this->courseid);
         $completed = 0;
@@ -123,8 +169,12 @@ class gradingscanner {
 
     }
 
-    // Function copied from bistate aggregator to avoid reference mazes.
-    private function grade_passed($grade) {
+    /**
+     * Check if a grade is considered passed according to the rules
+     * @param grade_grade $grade 
+     */
+    private function grade_passed($grade) : bool {
+        // Function copied from bistate aggregator to avoid reference mazes.
         global $DB;
         $table = "local_treestudyplan_gradecfg";
         // First determine if we have a grade_config for this scale or this maximum grade.