diff --git a/src/FactorGraphs/Factor.php b/src/FactorGraphs/Factor.php
index b0fbce6..2f1b1cf 100644
--- a/src/FactorGraphs/Factor.php
+++ b/src/FactorGraphs/Factor.php
@@ -8,12 +8,18 @@ use Exception;
 
 abstract class Factor implements \Stringable
 {
+    /**
+     * @var Message[] $messages
+     */
     private array $messages = [];
 
     private HashMap $messageToVariableBinding;
 
     private string $name;
 
+    /**
+     * @var Variable[] $variables
+     */
     private array $variables = [];
 
     protected function __construct(string $name)
@@ -64,7 +70,7 @@ abstract class Factor implements \Stringable
         return $this->updateMessageVariable($message, $variable);
     }
 
-    protected function updateMessageVariable(Message $message, Variable $variable)
+    protected function updateMessageVariable(Message $message, Variable $variable): float
     {
         throw new Exception();
     }
@@ -82,13 +88,9 @@ abstract class Factor implements \Stringable
 
     /**
      * Sends the ith message to the marginal and returns the log-normalization constant
-     *
-     * @param  $messageIndex
-     * @return
-     *
      * @throws Exception
      */
-    public function sendMessageIndex($messageIndex)
+    public function sendMessageIndex(int $messageIndex): float|int
     {
         Guard::argumentIsValidIndex($messageIndex, count($this->messages), 'messageIndex');
 
@@ -98,7 +100,7 @@ abstract class Factor implements \Stringable
         return $this->sendMessageVariable($message, $variable);
     }
 
-    abstract protected function sendMessageVariable(Message $message, Variable $variable);
+    abstract protected function sendMessageVariable(Message $message, Variable $variable): float|int;
 
     abstract public function createVariableToMessageBinding(Variable $variable);
 
diff --git a/src/FactorGraphs/FactorGraphLayer.php b/src/FactorGraphs/FactorGraphLayer.php
index cf2561c..168dc98 100644
--- a/src/FactorGraphs/FactorGraphLayer.php
+++ b/src/FactorGraphs/FactorGraphLayer.php
@@ -4,6 +4,9 @@ namespace DNW\Skills\FactorGraphs;
 
 abstract class FactorGraphLayer
 {
+    /**
+     * @var Factor[] $localFactors
+     */
     private array $localFactors = [];
 
     private array $outputVariablesGroups = [];
@@ -34,6 +37,9 @@ abstract class FactorGraphLayer
         return $this->outputVariablesGroups;
     }
 
+    /**
+     * @return Factor[]
+     */
     public function getLocalFactors(): array
     {
         return $this->localFactors;
diff --git a/src/PartialPlay.php b/src/PartialPlay.php
index 8f5d474..ad21385 100644
--- a/src/PartialPlay.php
+++ b/src/PartialPlay.php
@@ -4,7 +4,7 @@ namespace DNW\Skills;
 
 class PartialPlay
 {
-    public static function getPartialPlayPercentage($player)
+    public static function getPartialPlayPercentage(Player $player): float
     {
         // If the player doesn't support the interface, assume 1.0 == 100%
         $supportsPartialPlay = $player instanceof ISupportPartialPlay;
diff --git a/src/TrueSkill/FactorGraphTrueSkillCalculator.php b/src/TrueSkill/FactorGraphTrueSkillCalculator.php
index 2066e42..8c2c9fd 100644
--- a/src/TrueSkill/FactorGraphTrueSkillCalculator.php
+++ b/src/TrueSkill/FactorGraphTrueSkillCalculator.php
@@ -13,6 +13,7 @@ use DNW\Skills\PlayersRange;
 use DNW\Skills\RankSorter;
 use DNW\Skills\SkillCalculator;
 use DNW\Skills\SkillCalculatorSupportedOptions;
+use DNW\Skills\Team;
 use DNW\Skills\TeamsRange;
 use DNW\Skills\RatingContainer;
 
@@ -151,11 +152,9 @@ class FactorGraphTrueSkillCalculator extends SkillCalculator
         $playerAssignments = [];
         $totalPreviousPlayers = 0;
 
-        $teamAssignmentsListCount = is_countable($teamAssignmentsList) ? count($teamAssignmentsList) : 0;
-
         $currentColumn = 0;
 
-        for ($i = 0; $i < $teamAssignmentsListCount - 1; $i++) {
+        for ($i = 0; $i < count($teamAssignmentsList) - 1; $i++) {
             $currentTeam = $teamAssignmentsList[$i];
 
             // Need to add in 0's for all the previous players, since they're not
@@ -185,6 +184,6 @@ class FactorGraphTrueSkillCalculator extends SkillCalculator
             $currentColumn++;
         }
 
-        return Matrix::fromColumnValues($totalPlayers, $teamAssignmentsListCount - 1, $playerAssignments);
+        return Matrix::fromColumnValues($totalPlayers, count($teamAssignmentsList) - 1, $playerAssignments);
     }
 }
diff --git a/src/TrueSkill/Layers/IteratedTeamDifferencesInnerLayer.php b/src/TrueSkill/Layers/IteratedTeamDifferencesInnerLayer.php
index d8070e9..9db37b2 100644
--- a/src/TrueSkill/Layers/IteratedTeamDifferencesInnerLayer.php
+++ b/src/TrueSkill/Layers/IteratedTeamDifferencesInnerLayer.php
@@ -27,7 +27,7 @@ class IteratedTeamDifferencesInnerLayer extends TrueSkillFactorGraphLayer
         );
     }
 
-    public function buildLayer()
+    public function buildLayer(): void
     {
         $inputVariablesGroups = $this->getInputVariablesGroups();
         $this->TeamPerformancesToTeamPerformanceDifferencesLayer->setInputVariablesGroups($inputVariablesGroups);