diff --git a/app/code/Magento/CatalogInventory/Model/ProductCollectionStockCondition.php b/app/code/Magento/CatalogInventory/Model/ProductCollectionStockCondition.php
index 28af97ff3fe2b..fb2f3ec9f222e 100644
--- a/app/code/Magento/CatalogInventory/Model/ProductCollectionStockCondition.php
+++ b/app/code/Magento/CatalogInventory/Model/ProductCollectionStockCondition.php
@@ -6,7 +6,6 @@
 namespace Magento\CatalogInventory\Model;
 
 use Magento\Catalog\Model\CollectionConditionInterface;
-use Magento\Eav\Model\Entity\Collection\AbstractCollection;
 use Magento\Framework\Data\Collection\AbstractDb;
 use Magento\Framework\Data\CollectionModifierInterface;
 
diff --git a/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Item/StockItemCriteria.php b/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Item/StockItemCriteria.php
index 47359f970e93f..b93ff611c24aa 100644
--- a/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Item/StockItemCriteria.php
+++ b/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Item/StockItemCriteria.php
@@ -1,18 +1,18 @@
 <?php
 /**
- * Copyright 2015 Adobe
+ * Copyright 2014 Adobe
  * All Rights Reserved.
  */
 
 namespace Magento\CatalogInventory\Model\ResourceModel\Stock\Item;
 
+use Magento\CatalogInventory\Api\StockItemCriteriaInterface;
 use Magento\Framework\Data\AbstractCriteria;
-use Magento\CatalogInventory\Model\ResourceModel\Stock\Item\StockItemCriteriaMapper;
 
 /**
- * Class StockItemCriteria
+ * Class StockItemCriteria Resource model
  */
-class StockItemCriteria extends AbstractCriteria implements \Magento\CatalogInventory\Api\StockItemCriteriaInterface
+class StockItemCriteria extends AbstractCriteria implements StockItemCriteriaInterface
 {
     /**
      * @param string $mapper
@@ -80,10 +80,10 @@ public function setQtyFilter($comparisonMethod, $qty)
     /**
      * Add Criteria object
      *
-     * @param \Magento\CatalogInventory\Api\StockItemCriteriaInterface $criteria
+     * @param StockItemCriteriaInterface $criteria
      * @return bool
      */
-    public function addCriteria(\Magento\CatalogInventory\Api\StockItemCriteriaInterface $criteria)
+    public function addCriteria(StockItemCriteriaInterface $criteria)
     {
         $this->data[self::PART_CRITERIA_LIST]['list'][] = $criteria;
         return true;
diff --git a/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Status/StockStatusCriteria.php b/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Status/StockStatusCriteria.php
index 3f891da50e7e6..f59fcd1d53aca 100644
--- a/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Status/StockStatusCriteria.php
+++ b/app/code/Magento/CatalogInventory/Model/ResourceModel/Stock/Status/StockStatusCriteria.php
@@ -1,18 +1,18 @@
 <?php
 /**
- * Copyright 2015 Adobe
+ * Copyright 2014 Adobe
  * All Rights Reserved.
  */
 
 namespace Magento\CatalogInventory\Model\ResourceModel\Stock\Status;
 
+use Magento\CatalogInventory\Api\StockStatusCriteriaInterface;
 use Magento\Framework\Data\AbstractCriteria;
-use Magento\CatalogInventory\Model\ResourceModel\Stock\Status\StockStatusCriteriaMapper;
 
 /**
- * Class StockStatusCriteria
+ * Class StockStatusCriteria Resource model
  */
-class StockStatusCriteria extends AbstractCriteria implements \Magento\CatalogInventory\Api\StockStatusCriteriaInterface
+class StockStatusCriteria extends AbstractCriteria implements StockStatusCriteriaInterface
 {
     /**
      * @param string $mapper
@@ -24,7 +24,10 @@ public function __construct($mapper = '')
     }
 
     /**
-     * @inheritdoc
+     * Filter by scope(s)
+     *
+     * @param int $scope
+     * @return void
      */
     public function setScopeFilter($scope)
     {
@@ -32,7 +35,10 @@ public function setScopeFilter($scope)
     }
 
     /**
-     * @inheritdoc
+     * Add product(s) filter
+     *
+     * @param int $products
+     * @return void
      */
     public function setProductsFilter($products)
     {
@@ -40,7 +46,10 @@ public function setProductsFilter($products)
     }
 
     /**
-     * @inheritdoc
+     * Add filter by quantity
+     *
+     * @param float $qty
+     * @return void
      */
     public function setQtyFilter($qty)
     {
@@ -48,9 +57,12 @@ public function setQtyFilter($qty)
     }
 
     /**
-     * @inheritdoc
+     * Add Criteria object
+     *
+     * @param \Magento\CatalogInventory\Api\StockStatusCriteriaInterface $criteria
+     * @return void
      */
-    public function addCriteria(\Magento\CatalogInventory\Api\StockStatusCriteriaInterface $criteria)
+    public function addCriteria(StockStatusCriteriaInterface $criteria)
     {
         $this->data[self::PART_CRITERIA_LIST]['list'][] = $criteria;
     }
diff --git a/app/code/Magento/CatalogInventory/Model/StockRegistry.php b/app/code/Magento/CatalogInventory/Model/StockRegistry.php
index 6597b58942216..4eec4b9161cee 100644
--- a/app/code/Magento/CatalogInventory/Model/StockRegistry.php
+++ b/app/code/Magento/CatalogInventory/Model/StockRegistry.php
@@ -15,7 +15,7 @@
 use Magento\CatalogInventory\Model\Spi\StockRegistryProviderInterface;
 
 /**
- * Class StockRegistry
+ * Class Catalog StockRegistry
  *
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  */
@@ -68,6 +68,8 @@ public function __construct(
     }
 
     /**
+     * Get Stock data
+     *
      * @param int $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockInterface
      */
@@ -78,9 +80,11 @@ public function getStock($scopeId = null)
     }
 
     /**
+     * Get Stock Item data
+     *
      * @param int $productId
      * @param int $scopeId
-     * @return \Magento\CatalogInventory\Api\Data\StockItemInterface
+     * @return StockItemInterface
      */
     public function getStockItem($productId, $scopeId = null)
     {
@@ -89,9 +93,11 @@ public function getStockItem($productId, $scopeId = null)
     }
 
     /**
+     * Get Stock Item By SKU
+     *
      * @param string $productSku
      * @param int $scopeId
-     * @return \Magento\CatalogInventory\Api\Data\StockItemInterface
+     * @return StockItemInterface
      * @throws \Magento\Framework\Exception\NoSuchEntityException
      */
     public function getStockItemBySku($productSku, $scopeId = null)
@@ -102,6 +108,8 @@ public function getStockItemBySku($productSku, $scopeId = null)
     }
 
     /**
+     * Get Stock status
+     *
      * @param int $productId
      * @param int $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockStatusInterface
@@ -113,6 +121,8 @@ public function getStockStatus($productId, $scopeId = null)
     }
 
     /**
+     * Get Stock status by SKU
+     *
      * @param string $productSku
      * @param int $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockStatusInterface
@@ -127,6 +137,7 @@ public function getStockStatusBySku($productSku, $scopeId = null)
 
     /**
      * Retrieve Product stock status
+     *
      * @param int $productId
      * @param int $scopeId
      * @return int
@@ -139,8 +150,10 @@ public function getProductStockStatus($productId, $scopeId = null)
     }
 
     /**
+     * Get Product Stock status by SKU
+     *
      * @param string $productSku
-     * @param null $scopeId
+     * @param null|int $scopeId
      * @return int
      * @throws \Magento\Framework\Exception\NoSuchEntityException
      */
@@ -167,7 +180,7 @@ public function getLowStockItems($scopeId, $qty, $currentPage = 1, $pageSize = 0
     /**
      * @inheritdoc
      */
-    public function updateStockItemBySku($productSku, \Magento\CatalogInventory\Api\Data\StockItemInterface $stockItem)
+    public function updateStockItemBySku($productSku, StockItemInterface $stockItem)
     {
         $productId = $this->resolveProductId($productSku);
         $websiteId = $stockItem->getWebsiteId() ?: null;
@@ -182,6 +195,8 @@ public function updateStockItemBySku($productSku, \Magento\CatalogInventory\Api\
     }
 
     /**
+     * Resolve the Product Id
+     *
      * @param string $productSku
      * @return int
      * @throws \Magento\Framework\Exception\NoSuchEntityException
diff --git a/app/code/Magento/CatalogInventory/Model/StockRegistryProvider.php b/app/code/Magento/CatalogInventory/Model/StockRegistryProvider.php
index fea503f49efe0..b68f974867dc2 100644
--- a/app/code/Magento/CatalogInventory/Model/StockRegistryProvider.php
+++ b/app/code/Magento/CatalogInventory/Model/StockRegistryProvider.php
@@ -15,10 +15,9 @@
 use Magento\CatalogInventory\Api\StockCriteriaInterfaceFactory;
 use Magento\CatalogInventory\Api\StockItemCriteriaInterfaceFactory;
 use Magento\CatalogInventory\Api\StockStatusCriteriaInterfaceFactory;
-use Magento\Store\Model\StoreManagerInterface;
 
 /**
- * Class StockRegistryProvider
+ * Class Catalog StockRegistryProvider
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  */
 class StockRegistryProvider implements StockRegistryProviderInterface
@@ -108,6 +107,8 @@ public function __construct(
     }
 
     /**
+     * Get Stock
+     *
      * @param int|null $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockInterface
      */
@@ -129,6 +130,8 @@ public function getStock($scopeId)
     }
 
     /**
+     * Get Stock Item
+     *
      * @param int $productId
      * @param int $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockItemInterface
@@ -151,6 +154,8 @@ public function getStockItem($productId, $scopeId)
     }
 
     /**
+     * Get Stock Status
+     *
      * @param int $productId
      * @param int $scopeId
      * @return \Magento\CatalogInventory\Api\Data\StockStatusInterface
@@ -174,6 +179,8 @@ public function getStockStatus($productId, $scopeId)
     }
 
     /**
+     * Get Stock Registry Storage
+     *
      * @return StockRegistryStorage
      */
     private function getStockRegistryStorage()
diff --git a/app/code/Magento/CatalogInventory/Setup/Patch/Data/CreateDefaultStock.php b/app/code/Magento/CatalogInventory/Setup/Patch/Data/CreateDefaultStock.php
index 5deea1ed0b8df..292fc4dc20bf4 100644
--- a/app/code/Magento/CatalogInventory/Setup/Patch/Data/CreateDefaultStock.php
+++ b/app/code/Magento/CatalogInventory/Setup/Patch/Data/CreateDefaultStock.php
@@ -8,14 +8,12 @@
 
 use Magento\Eav\Setup\EavSetup;
 use Magento\Eav\Setup\EavSetupFactory;
-use Magento\Framework\App\ResourceConnection;
 use Magento\Framework\Setup\ModuleDataSetupInterface;
 use Magento\Framework\Setup\Patch\DataPatchInterface;
 use Magento\Framework\Setup\Patch\PatchVersionInterface;
 
 /**
- * Class CreateDefaultStock
- * @package Magento\CatalogInventory\Setup\Patch
+ * Class CreateDefaultStock patch
  */
 class CreateDefaultStock implements DataPatchInterface, PatchVersionInterface
 {
@@ -43,7 +41,13 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * Run code inside patch
+     * If code fails, patch must be reverted, in case when we are speaking about schema - then under revert
+     * means run PatchInterface::revert()
+     *
+     * If we speak about data, under revert means: $transaction->rollback()
+     *
+     * @return void
      */
     public function apply()
     {
@@ -66,7 +70,7 @@ public function apply()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getDependencies()
     {
@@ -74,7 +78,7 @@ public static function getDependencies()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getVersion()
     {
@@ -82,7 +86,7 @@ public static function getVersion()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getAliases()
     {
diff --git a/app/code/Magento/CatalogInventory/Setup/Patch/Data/UpdateStockItemsWebsite.php b/app/code/Magento/CatalogInventory/Setup/Patch/Data/UpdateStockItemsWebsite.php
index 6580c4651f377..e39ad4a236ec6 100644
--- a/app/code/Magento/CatalogInventory/Setup/Patch/Data/UpdateStockItemsWebsite.php
+++ b/app/code/Magento/CatalogInventory/Setup/Patch/Data/UpdateStockItemsWebsite.php
@@ -7,14 +7,12 @@
 namespace Magento\CatalogInventory\Setup\Patch\Data;
 
 use Magento\CatalogInventory\Model\Indexer\Stock\Processor;
-use Magento\Framework\App\ResourceConnection;
 use Magento\Framework\Setup\ModuleDataSetupInterface;
 use Magento\Framework\Setup\Patch\DataPatchInterface;
 use Magento\Framework\Setup\Patch\PatchVersionInterface;
 
 /**
- * Class UpdateStockItemsWebsite
- * @package Magento\CatalogInventory\Setup\Patch
+ * Class UpdateStockItemsWebsite patch
  */
 class UpdateStockItemsWebsite implements DataPatchInterface, PatchVersionInterface
 {
@@ -58,7 +56,13 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * Run code inside patch
+     * If code fails, patch must be reverted, in case when we are speaking about schema - then under revert
+     * means run PatchInterface::revert()
+     *
+     * If we speak about data, under revert means: $transaction->rollback()
+     *
+     * @return void
      */
     public function apply()
     {
@@ -71,7 +75,7 @@ public function apply()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getDependencies()
     {
@@ -81,7 +85,7 @@ public static function getDependencies()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public static function getVersion()
     {
@@ -89,7 +93,7 @@ public static function getVersion()
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritdoc
      */
     public function getAliases()
     {