diff --git a/app/code/Magento/Customer/Controller/RegistryConstants.php b/app/code/Magento/Customer/Controller/RegistryConstants.php
index b56acc634f4c6..b89c2d003160d 100644
--- a/app/code/Magento/Customer/Controller/RegistryConstants.php
+++ b/app/code/Magento/Customer/Controller/RegistryConstants.php
@@ -3,11 +3,14 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Customer\Controller;
 
 /**
  * Declarations of core registry keys used by the Customer module
  *
+ * @api
  */
 class RegistryConstants
 {
diff --git a/app/code/Magento/Customer/Model/Context.php b/app/code/Magento/Customer/Model/Context.php
index 63d1fc36b4539..7b82a3dd98d31 100644
--- a/app/code/Magento/Customer/Model/Context.php
+++ b/app/code/Magento/Customer/Model/Context.php
@@ -3,8 +3,15 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Customer\Model;
 
+/**
+ * Class Context
+ *
+ * @api
+ */
 class Context
 {
     /**
diff --git a/app/code/Magento/Sales/Model/ResourceModel/Order/Collection/Factory.php b/app/code/Magento/Sales/Model/ResourceModel/Order/Collection/Factory.php
index 6a622a3dcf85e..da7ea8ca18bfa 100644
--- a/app/code/Magento/Sales/Model/ResourceModel/Order/Collection/Factory.php
+++ b/app/code/Magento/Sales/Model/ResourceModel/Order/Collection/Factory.php
@@ -3,9 +3,13 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Sales\Model\ResourceModel\Order\Collection;
 
 /**
+ * Class Factory
+ *
  * @api
  */
 class Factory
diff --git a/app/code/Magento/Sales/Model/ResourceModel/Order/CollectionFactory.php b/app/code/Magento/Sales/Model/ResourceModel/Order/CollectionFactory.php
index d1a88f5826b91..4e0abb81b7c64 100644
--- a/app/code/Magento/Sales/Model/ResourceModel/Order/CollectionFactory.php
+++ b/app/code/Magento/Sales/Model/ResourceModel/Order/CollectionFactory.php
@@ -8,6 +8,8 @@
 
 /**
  * Class CollectionFactory
+ *
+ * @api
  */
 class CollectionFactory implements CollectionFactoryInterface
 {
diff --git a/app/code/Magento/Shipping/Model/Carrier/CarrierInterface.php b/app/code/Magento/Shipping/Model/Carrier/CarrierInterface.php
index 0cdbd5c078567..7fc49dd3f9b91 100644
--- a/app/code/Magento/Shipping/Model/Carrier/CarrierInterface.php
+++ b/app/code/Magento/Shipping/Model/Carrier/CarrierInterface.php
@@ -3,11 +3,14 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Shipping\Model\Carrier;
 
 /**
  * Interface \Magento\Shipping\Model\Carrier\CarrierInterface
  *
+ * @api
  */
 interface CarrierInterface
 {
diff --git a/app/code/Magento/Ui/Component/Layout/Tabs/TabInterface.php b/app/code/Magento/Ui/Component/Layout/Tabs/TabInterface.php
index bf977d33ad7e8..0eeab9a8204ce 100644
--- a/app/code/Magento/Ui/Component/Layout/Tabs/TabInterface.php
+++ b/app/code/Magento/Ui/Component/Layout/Tabs/TabInterface.php
@@ -3,6 +3,8 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Ui\Component\Layout\Tabs;
 
 /**
diff --git a/app/code/Magento/Widget/Block/BlockInterface.php b/app/code/Magento/Widget/Block/BlockInterface.php
index eff9a0b26b528..7650f2cf0e2e9 100644
--- a/app/code/Magento/Widget/Block/BlockInterface.php
+++ b/app/code/Magento/Widget/Block/BlockInterface.php
@@ -3,11 +3,13 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 /**
  * Widget Block Interface
  *
  * @author      Magento Core Team <core@magentocommerce.com>
+ * @api
  */
 namespace Magento\Widget\Block;
 
diff --git a/lib/internal/Magento/Framework/Api/AbstractSimpleObject.php b/lib/internal/Magento/Framework/Api/AbstractSimpleObject.php
index 9cc0ddab3bfcb..59a01f6f99e13 100644
--- a/lib/internal/Magento/Framework/Api/AbstractSimpleObject.php
+++ b/lib/internal/Magento/Framework/Api/AbstractSimpleObject.php
@@ -3,11 +3,15 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\Api;
 
 /**
  * Base Class for simple data Objects
  * @SuppressWarnings(PHPMD.NumberOfChildren)
+ *
+ * @api
  */
 abstract class AbstractSimpleObject
 {
diff --git a/lib/internal/Magento/Framework/App/Filesystem/DirectoryList.php b/lib/internal/Magento/Framework/App/Filesystem/DirectoryList.php
index ce150b00a6665..423719c87c4b6 100644
--- a/lib/internal/Magento/Framework/App/Filesystem/DirectoryList.php
+++ b/lib/internal/Magento/Framework/App/Filesystem/DirectoryList.php
@@ -3,12 +3,16 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\App\Filesystem;
 
 use Magento\Framework\Code\Generator\Io;
 
 /**
  * A Magento application specific list of directories
+ *
+ * @api
  */
 class DirectoryList extends \Magento\Framework\Filesystem\DirectoryList
 {
diff --git a/lib/internal/Magento/Framework/App/Http/Context.php b/lib/internal/Magento/Framework/App/Http/Context.php
index 79a15110234cd..b3fa5a5cca67b 100644
--- a/lib/internal/Magento/Framework/App/Http/Context.php
+++ b/lib/internal/Magento/Framework/App/Http/Context.php
@@ -3,6 +3,8 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\App\Http;
 
 use Magento\Framework\App\ObjectManager;
@@ -10,6 +12,8 @@
 
 /**
  * Context data for requests
+ *
+ * @api
  */
 class Context
 {
diff --git a/lib/internal/Magento/Framework/App/Response/Http/FileFactory.php b/lib/internal/Magento/Framework/App/Response/Http/FileFactory.php
index d599f91ca8ca4..a54a19aa9907b 100644
--- a/lib/internal/Magento/Framework/App/Response/Http/FileFactory.php
+++ b/lib/internal/Magento/Framework/App/Response/Http/FileFactory.php
@@ -11,6 +11,8 @@
 
 /**
  * Class FileFactory serves to declare file content in response for download.
+ *
+ * @api
  */
 class FileFactory
 {
diff --git a/lib/internal/Magento/Framework/Controller/Result/JsonFactory.php b/lib/internal/Magento/Framework/Controller/Result/JsonFactory.php
index 1d315df8babdd..cc54ec44b754c 100644
--- a/lib/internal/Magento/Framework/Controller/Result/JsonFactory.php
+++ b/lib/internal/Magento/Framework/Controller/Result/JsonFactory.php
@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\Controller\Result;
 
diff --git a/lib/internal/Magento/Framework/Controller/Result/Raw.php b/lib/internal/Magento/Framework/Controller/Result/Raw.php
index 6355029af4da5..6ccea7b2d0c4f 100644
--- a/lib/internal/Magento/Framework/Controller/Result/Raw.php
+++ b/lib/internal/Magento/Framework/Controller/Result/Raw.php
@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\Controller\Result;
 
@@ -12,6 +13,8 @@
 /**
  * A result that contains raw response - may be good for passing through files,
  * returning result of downloads or some other binary contents
+ *
+ * @api
  */
 class Raw extends AbstractResult
 {
diff --git a/lib/internal/Magento/Framework/Data/FormFactory.php b/lib/internal/Magento/Framework/Data/FormFactory.php
index eaf98903e64bb..077c23875d4ac 100644
--- a/lib/internal/Magento/Framework/Data/FormFactory.php
+++ b/lib/internal/Magento/Framework/Data/FormFactory.php
@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\Data;
 
diff --git a/lib/internal/Magento/Framework/Filesystem/DirectoryList.php b/lib/internal/Magento/Framework/Filesystem/DirectoryList.php
index b3ab51b948109..7d74c2f127095 100644
--- a/lib/internal/Magento/Framework/Filesystem/DirectoryList.php
+++ b/lib/internal/Magento/Framework/Filesystem/DirectoryList.php
@@ -8,6 +8,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\Filesystem;
 
@@ -21,6 +22,8 @@
  * This object is intended to be immutable (a "value object").
  * The defaults are pre-defined and can be modified only by inheritors of this class.
  * Through the constructor, it is possible to inject custom paths or URL paths, but impossible to inject new types.
+ *
+ * @api
  */
 class DirectoryList
 {
diff --git a/lib/internal/Magento/Framework/Logger/Handler/Base.php b/lib/internal/Magento/Framework/Logger/Handler/Base.php
index 07dfd3f0963ab..af385bd6650ed 100644
--- a/lib/internal/Magento/Framework/Logger/Handler/Base.php
+++ b/lib/internal/Magento/Framework/Logger/Handler/Base.php
@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\Logger\Handler;
 
@@ -13,6 +14,8 @@
 
 /**
  * Base stream handler
+ *
+ * @api
  */
 class Base extends StreamHandler
 {
diff --git a/lib/internal/Magento/Framework/View/Element/Html/Select.php b/lib/internal/Magento/Framework/View/Element/Html/Select.php
index 09b5d7f2e821c..723cad9a8b226 100644
--- a/lib/internal/Magento/Framework/View/Element/Html/Select.php
+++ b/lib/internal/Magento/Framework/View/Element/Html/Select.php
@@ -3,10 +3,14 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\View\Element\Html;
 
 /**
  * HTML select element block
+ *
+ * @api
  */
 class Select extends \Magento\Framework\View\Element\AbstractBlock
 {
diff --git a/lib/internal/Magento/Framework/View/Element/UiComponent/ContextInterface.php b/lib/internal/Magento/Framework/View/Element/UiComponent/ContextInterface.php
index 78393e661d609..48d6dee29aa24 100644
--- a/lib/internal/Magento/Framework/View/Element/UiComponent/ContextInterface.php
+++ b/lib/internal/Magento/Framework/View/Element/UiComponent/ContextInterface.php
@@ -3,6 +3,8 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\View\Element\UiComponent;
 
 use Magento\Framework\View\Element\UiComponentInterface;
diff --git a/lib/internal/Magento/Framework/View/Element/UiComponent/Control/ButtonProviderInterface.php b/lib/internal/Magento/Framework/View/Element/UiComponent/Control/ButtonProviderInterface.php
index eab6dbfae1122..00395b83082ce 100644
--- a/lib/internal/Magento/Framework/View/Element/UiComponent/Control/ButtonProviderInterface.php
+++ b/lib/internal/Magento/Framework/View/Element/UiComponent/Control/ButtonProviderInterface.php
@@ -3,6 +3,8 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\View\Element\UiComponent\Control;
 
 /**
diff --git a/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/DataProvider.php b/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/DataProvider.php
index baa4e94eed978..fba50ad2c0b7b 100644
--- a/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/DataProvider.php
+++ b/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/DataProvider.php
@@ -3,6 +3,8 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\View\Element\UiComponent\DataProvider;
 
 use Magento\Framework\Api\FilterBuilder;
@@ -14,6 +16,8 @@
 
 /**
  * Class DataProvider
+ *
+ * @api
  */
 class DataProvider implements DataProviderInterface
 {
diff --git a/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/SearchResult.php b/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/SearchResult.php
index 32334e89c5876..623d33a78ee9d 100644
--- a/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/SearchResult.php
+++ b/lib/internal/Magento/Framework/View/Element/UiComponent/DataProvider/SearchResult.php
@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 namespace Magento\Framework\View\Element\UiComponent\DataProvider;
 
@@ -19,6 +20,7 @@
  * Class SearchResult
  * Generic Search Result
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ * @api
  */
 class SearchResult extends AbstractCollection implements Api\Search\SearchResultInterface
 {
diff --git a/lib/internal/Magento/Framework/View/LayoutFactory.php b/lib/internal/Magento/Framework/View/LayoutFactory.php
index b33a97cfaad80..9ad8fc7f98b16 100644
--- a/lib/internal/Magento/Framework/View/LayoutFactory.php
+++ b/lib/internal/Magento/Framework/View/LayoutFactory.php
@@ -3,10 +3,14 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
+
 namespace Magento\Framework\View;
 
 /**
  * Factory class for Layout
+ *
+ * @api
  */
 class LayoutFactory
 {