diff --git a/application/Espo/Core/MassAction/Actions/MassConvertCurrency.php b/application/Espo/Core/MassAction/Actions/MassConvertCurrency.php
index bece2ba946..3d938fc56f 100644
--- a/application/Espo/Core/MassAction/Actions/MassConvertCurrency.php
+++ b/application/Espo/Core/MassAction/Actions/MassConvertCurrency.php
@@ -67,7 +67,7 @@ class MassConvertCurrency implements MassAction
 
     protected CurrencyConverter $currencyConverter;
 
-    private $user;
+    private User $user;
 
     public function __construct(
         QueryBuilder $queryBuilder,
@@ -161,6 +161,9 @@ class MassConvertCurrency implements MassAction
         return Result::fromArray($result);
     }
 
+    /**
+     * @param string[] $fieldList
+     */
     protected function convertEntity(
         Entity $entity,
         array $fieldList,
@@ -218,6 +221,9 @@ class MassConvertCurrency implements MassAction
         return CurrencyRates::fromArray($ratesArray);
     }
 
+    /**
+     * @return string[]
+     */
     protected function getFieldList(string $entityType, Data $data): array
     {
         $forbiddenFieldList = $this->acl->getScopeForbiddenFieldList($entityType, 'edit');
diff --git a/application/Espo/Core/MassAction/Actions/MassUpdate.php b/application/Espo/Core/MassAction/Actions/MassUpdate.php
index 62228fc5aa..dfdc5d6a1b 100644
--- a/application/Espo/Core/MassAction/Actions/MassUpdate.php
+++ b/application/Espo/Core/MassAction/Actions/MassUpdate.php
@@ -172,6 +172,9 @@ class MassUpdate implements MassAction
         return Result::fromArray($result);
     }
 
+    /**
+     * @param string[] $fieldToCopyList
+     */
     protected function prepareItemValueMap(
         string $entityType,
         stdClass $valueMap,
@@ -264,6 +267,9 @@ class MassUpdate implements MassAction
         $valueMap->$idsAttribute = $copiedIds;
     }
 
+    /**
+     * @return string[]
+     */
     protected function detectFieldToCopyList(string $entityType, stdClass $valueMap): array
     {
         $resultFieldList = [];
diff --git a/application/Espo/Core/MassAction/MassActionFactory.php b/application/Espo/Core/MassAction/MassActionFactory.php
index cead52db76..d0e8da22dd 100644
--- a/application/Espo/Core/MassAction/MassActionFactory.php
+++ b/application/Espo/Core/MassAction/MassActionFactory.php
@@ -42,11 +42,11 @@ use Espo\Core\Binding\BindingContainerBuilder;
 
 class MassActionFactory
 {
-    private $metadata;
+    private Metadata $metadata;
 
-    private $injectableFactory;
+    private InjectableFactory $injectableFactory;
 
-    private $aclManager;
+    private AclManager $aclManager;
 
     public function __construct(Metadata $metadata, InjectableFactory $injectableFactory, AclManager $aclManager)
     {
@@ -86,6 +86,11 @@ class MassActionFactory
         return $this->injectableFactory->createWithBinding($className, $bindingContainer);
     }
 
+    /**
+     * @param array<string,mixed> $with
+     * @deprecated
+     * @todo Remove.
+     */
     public function createWith(string $action, string $entityType, array $with): MassAction
     {
         $className = $this->getClassName($action, $entityType);
@@ -97,6 +102,9 @@ class MassActionFactory
         return $this->injectableFactory->createWith($className, $with);
     }
 
+    /**
+     * @return ?class-string
+     */
     private function getClassName(string $action, string $entityType): ?string
     {
         $className = $this->getEntityTypeClassName($action, $entityType);
@@ -110,6 +118,9 @@ class MassActionFactory
         );
     }
 
+    /**
+     * @return ?class-string
+     */
     private function getEntityTypeClassName(string $action, string $entityType): ?string
     {
         return $this->metadata->get(
diff --git a/application/Espo/Core/MassAction/Params.php b/application/Espo/Core/MassAction/Params.php
index 61bc07d11c..203df95688 100644
--- a/application/Espo/Core/MassAction/Params.php
+++ b/application/Espo/Core/MassAction/Params.php
@@ -35,21 +35,26 @@ use RuntimeException;
 
 class Params
 {
-    private $entityType;
+    private string $entityType;
 
-    private $ids;
+    /**
+     * @var ?string[]
+     */
+    private $ids = null;
 
-    private $searchParams;
+    private ?SearchParams $searchParams = null;
 
-    private function __construct()
-    {
-    }
+    private function __construct() {}
 
     public function getEntityType(): string
     {
         return $this->entityType;
     }
 
+    /**
+     * @return string[]
+     * @throws RuntimeException
+     */
     public function getIds(): array
     {
         if (!$this->ids) {
@@ -73,6 +78,9 @@ class Params
         return !is_null($this->ids);
     }
 
+    /**
+     * @param string[] $ids
+     */
     public static function createWithIds(string $entityType, array $ids): self
     {
         return self::fromRaw([
@@ -86,7 +94,6 @@ class Params
         $obj = new self();
 
         $obj->entityType = $entityType;
-
         $obj->searchParams = $searchParams;
 
         return $obj;
@@ -95,18 +102,28 @@ class Params
     /**
      * Create from raw params.
      *
+     * @param array{
+     *   entityType?: string,
+     *   where?: array<int,array<string,mixed>>,
+     *   ids?: ?string[],
+     *   searchParams?: ?array<string,mixed>,
+     * } $params
      * @throws RuntimeException
      */
     public static function fromRaw(array $params, ?string $entityType = null): self
     {
+        /** @var array<string,mixed> $params */
+
         $obj = new self();
 
-        $obj->entityType = $entityType ?? $params['entityType'] ?? null;
+        $passedEntityType = $entityType ?? $params['entityType'] ?? null;
 
-        if (!$obj->entityType) {
+        if (!$passedEntityType) {
             throw new RuntimeException("No 'entityType'.");
         }
 
+        $obj->entityType = $passedEntityType;
+
         $where = $params['where'] ?? null;
         $ids = $params['ids'] ?? null;
 
@@ -168,7 +185,11 @@ class Params
     }
 
     /**
-     * @return array
+     * @return array{
+     *   entityType: ?string,
+     *   ids: ?string[],
+     *   searchParams: string,
+     * }
      */
     public function __serialize(): array
     {
@@ -179,6 +200,13 @@ class Params
         ];
     }
 
+    /**
+     * @param array{
+     *   entityType: ?string,
+     *   ids: ?string[],
+     *   searchParams: string,
+     * } $data
+     */
     public function __unserialize(array $data): void
     {
         $this->entityType = $data['entityType'];
diff --git a/application/Espo/Core/MassAction/Result.php b/application/Espo/Core/MassAction/Result.php
index e99678277d..8d051e3c1b 100644
--- a/application/Espo/Core/MassAction/Result.php
+++ b/application/Espo/Core/MassAction/Result.php
@@ -33,11 +33,17 @@ use RuntimeException;
 
 class Result
 {
+    private ?int $count = null;
+
+    /**
+     * @var ?string[]
+     */
     private $ids = null;
 
-    private $count = null;
-
-    public function __construct(int $count, ?array $ids = null)
+    /**
+     * @param ?string[] $ids
+     */
+    public function __construct(?int $count, ?array $ids = null)
     {
         $this->count = $count;
         $this->ids = $ids;
@@ -53,6 +59,9 @@ class Result
         return $this->count !== null;
     }
 
+    /**
+     * @return string[]
+     */
     public function getIds(): array
     {
         if (!$this->hasIds()) {
@@ -78,6 +87,12 @@ class Result
         ]);
     }
 
+    /**
+     * @param array{
+     *   count?: ?int,
+     *   ids?: ?string[],
+     * } $data
+     */
     public static function fromArray(array $data): self
     {
         $obj = new self(