diff --git a/README.md b/README.md
index 7d4f12e..3ee277f 100644
--- a/README.md
+++ b/README.md
@@ -7,3 +7,240 @@
 ```
 composer require wearerequired/common-php
 ```
+
+## Example
+
+```php
+/**
+ * Bootstraps post type integrations.
+ */
+function bootstrap(): void {
+	add_action( 'init', __NAMESPACE__ . '\register_post_types' );
+	add_action( 'init', __NAMESPACE__ . '\register_post_meta' );
+	add_action( 'init', __NAMESPACE__ . '\register_taxonomies' );
+	add_action( 'init', __NAMESPACE__ . '\register_taxonomy_for_object_types', 11 );
+}
+
+/**
+ * Registers custom post types.
+ */
+function register_post_types() {
+	$post_types = new Container();
+
+	$post_types->add( Profession::NAME, new Profession() );
+	$post_types->add( School::NAME, new School() );
+	$post_types->add( Office::NAME, new Office() );
+	$post_types->add( Event::NAME, new Event() );
+	$post_types->add( Apprenticeship::NAME, new Apprenticeship() );
+	$post_types->add( TrialApprenticeship::NAME, new TrialApprenticeship() );
+	$post_types->add( Organization::NAME, new Organization() );
+
+	$post_types->bootstrap();
+}
+
+/**
+ * Registers post meta.
+ */
+function register_post_meta() {
+	$post_meta = new Container();
+
+	$post_meta->add( PostMeta\ImportID::KEY, new PostMeta\ImportID() );
+	$post_meta->add( PostMeta\ImportTimestamp::KEY, new PostMeta\ImportTimestamp() );
+
+	$post_meta->add( PostMeta\SchoolOfficeID::KEY, new PostMeta\SchoolOfficeID() );
+	$post_meta->add( PostMeta\SchoolTelNumber::KEY, new PostMeta\SchoolTelNumber() );
+	$post_meta->add( PostMeta\SchoolEmail::KEY, new PostMeta\SchoolEmail() );
+
+	$post_meta->add( PostMeta\OfficeStreet::KEY, new PostMeta\OfficeStreet() );
+	$post_meta->add( PostMeta\OfficePOBox::KEY, new PostMeta\OfficePOBox() );
+	$post_meta->add( PostMeta\OfficeEmail::KEY, new PostMeta\OfficeEmail() );
+	$post_meta->add( PostMeta\OfficeTelNumber::KEY, new PostMeta\OfficeTelNumber() );
+	$post_meta->add( PostMeta\OfficeFax::KEY, new PostMeta\OfficeFax() );
+	$post_meta->add( PostMeta\OfficeContactURL::KEY, new PostMeta\OfficeContactURL() );
+	$post_meta->add( PostMeta\OfficeOpeningHours::KEY, new PostMeta\OfficeOpeningHours() );
+	$post_meta->add( PostMeta\OfficeSendCopyToConsultant::KEY, new PostMeta\OfficeSendCopyToConsultant() );
+
+	$post_meta->add( PostMeta\EventAdditionalInfo::KEY, new PostMeta\EventAdditionalInfo() );
+	$post_meta->add( PostMeta\EventAddress::KEY, new PostMeta\EventAddress() );
+	$post_meta->add( PostMeta\EventAuthor::KEY, new PostMeta\EventAuthor() );
+	$post_meta->add( PostMeta\EventCity::KEY, new PostMeta\EventCity() );
+	$post_meta->add( PostMeta\EventCode::KEY, new PostMeta\EventCode() );
+	$post_meta->add( PostMeta\EventCreator::KEY, new PostMeta\EventCreator() );
+	$post_meta->add( PostMeta\EventDepartment::KEY, new PostMeta\EventDepartment() );
+	$post_meta->add( PostMeta\EventFeeInfoNoFees::KEY, new PostMeta\EventFeeInfoNoFees() );
+	$post_meta->add( PostMeta\EventFeeInfoFee::KEY, new PostMeta\EventFeeInfoFee() );
+	$post_meta->add( PostMeta\EventFeeInfoCurrency::KEY, new PostMeta\EventFeeInfoCurrency() );
+	$post_meta->add( PostMeta\EventFeeInfoDescription::KEY, new PostMeta\EventFeeInfoDescription() );
+	$post_meta->add( PostMeta\EventGuideDescr::KEY, new PostMeta\EventGuideDescr() );
+	$post_meta->add( PostMeta\EventGuideFirstname::KEY, new PostMeta\EventGuideFirstname() );
+	$post_meta->add( PostMeta\EventGuideLastname::KEY, new PostMeta\EventGuideLastname() );
+	$post_meta->add( PostMeta\EventHostCity::KEY, new PostMeta\EventHostCity() );
+	$post_meta->add( PostMeta\EventHostLastname::KEY, new PostMeta\EventHostLastname() );
+	$post_meta->add( PostMeta\EventHostRegion::KEY, new PostMeta\EventHostRegion() );
+	$post_meta->add( PostMeta\EventHostType::KEY, new PostMeta\EventHostType() );
+	$post_meta->add( PostMeta\EventHostZip::KEY, new PostMeta\EventHostZip() );
+	$post_meta->add( PostMeta\EventHostPhone::KEY, new PostMeta\EventHostPhone() );
+	$post_meta->add( PostMeta\EventHostMail::KEY, new PostMeta\EventHostMail() );
+	$post_meta->add( PostMeta\EventHostWebsite::KEY, new PostMeta\EventHostWebsite() );
+	$post_meta->add( PostMeta\EventLocation::KEY, new PostMeta\EventLocation() );
+	$post_meta->add( PostMeta\EventOrgDepartment::KEY, new PostMeta\EventOrgDepartment() );
+	$post_meta->add( PostMeta\EventRegion::KEY, new PostMeta\EventRegion() );
+	$post_meta->add( PostMeta\EventRegistrationLink::KEY, new PostMeta\EventRegistrationLink() );
+	$post_meta->add( PostMeta\EventRegistrationMail::KEY, new PostMeta\EventRegistrationMail() );
+	$post_meta->add( PostMeta\EventRegistrationName::KEY, new PostMeta\EventRegistrationName() );
+	$post_meta->add( PostMeta\EventHasRegistration::KEY, new PostMeta\EventHasRegistration() );
+	$post_meta->add( PostMeta\EventRegistrationPhone::KEY, new PostMeta\EventRegistrationPhone() );
+	$post_meta->add( PostMeta\EventSeatsMax::KEY, new PostMeta\EventSeatsMax() );
+	$post_meta->add( PostMeta\EventSeatsMin::KEY, new PostMeta\EventSeatsMin() );
+	$post_meta->add( PostMeta\EventSeatsAvailable::KEY, new PostMeta\EventSeatsAvailable() );
+	$post_meta->add( PostMeta\EventSpeakers::KEY, new PostMeta\EventSpeakers() );
+	$post_meta->add( PostMeta\EventUnid::KEY, new PostMeta\EventUnid() );
+	$post_meta->add( PostMeta\EventZip::KEY, new PostMeta\EventZip() );
+	$post_meta->add( PostMeta\EventDateStart::KEY, new PostMeta\EventDateStart() );
+	$post_meta->add( PostMeta\EventDateEnd::KEY, new PostMeta\EventDateEnd() );
+	$post_meta->add( PostMeta\EventDates::KEY, new PostMeta\EventDates() );
+	$post_meta->add( PostMeta\EventIsOnline::KEY, new PostMeta\EventIsOnline() );
+	$post_meta->add( PostMeta\EventTargetAudience::KEY, new PostMeta\EventTargetAudience() );
+	$post_meta->add( PostMeta\EventSwissdocIDs::KEY, new PostMeta\EventSwissdocIDs() );
+
+	$post_meta->add( PostMeta\SwissdocNumber::KEY, new PostMeta\SwissdocNumber() );
+
+	$post_meta->add( PostMeta\Zip::KEY, new PostMeta\Zip() );
+	$post_meta->add( PostMeta\City::KEY, new PostMeta\City() );
+	$post_meta->add( PostMeta\Lat::KEY, new PostMeta\Lat() );
+	$post_meta->add( PostMeta\Lng::KEY, new PostMeta\Lng() );
+
+	$post_meta->add( PostMeta\ProfessionSNI::KEY, new PostMeta\ProfessionSNI() );
+	$post_meta->add( PostMeta\ProfessionCompletedApprenticeshipContracts::KEY, new PostMeta\ProfessionCompletedApprenticeshipContracts() );
+	$post_meta->add( PostMeta\ProfessionVideoURLs::KEY, new PostMeta\ProfessionVideoURLs() );
+	$post_meta->add( PostMeta\ProfessionPodcastURLs::KEY, new PostMeta\ProfessionPodcastURLs() );
+	$post_meta->add( PostMeta\ProfessionSkipImport::KEY, new PostMeta\ProfessionSkipImport() );
+	$post_meta->add( PostMeta\ProfessionSchoolRequirementsURL::KEY, new PostMeta\ProfessionSchoolRequirementsURL() );
+	$post_meta->add( PostMeta\ProfessionHint::KEY, new PostMeta\ProfessionHint() );
+	$post_meta->add( PostMeta\ProfessionForeignLanguage::KEY, new PostMeta\ProfessionForeignLanguage() );
+
+	$post_meta->add( PostMeta\OrganizationLogoURL::KEY, new PostMeta\OrganizationLogoURL() );
+
+	$post_meta->bootstrap();
+}
+
+/**
+ * Registers custom taxonomies.
+ */
+function register_taxonomies(): void {
+	$taxonomies = new Container();
+
+	$taxonomies->add( ProfessionField::NAME, new ProfessionField() );
+	$taxonomies->add( ProfessionInterest::NAME, new ProfessionInterest() );
+	$taxonomies->add( ProfessionSector::NAME, new ProfessionSector() );
+	$taxonomies->add( ProfessionAlternativeTitle::NAME, new ProfessionAlternativeTitle() );
+	$taxonomies->add( ProfessionDuration::NAME, new ProfessionDuration() );
+	$taxonomies->add( ProfessionQualification::NAME, new ProfessionQualification() );
+	$taxonomies->add( ProfessionBilingualEducation::NAME, new ProfessionBilingualEducation() );
+	$taxonomies->add( EventSpeaker::NAME, new EventSpeaker() );
+	$taxonomies->add( EventAudience::NAME, new EventAudience() );
+	$taxonomies->add( EventTopic::NAME, new EventTopic() );
+	$taxonomies->add( EventStatus::NAME, new EventStatus() );
+	$taxonomies->add( Swissdoc::NAME, new Swissdoc() );
+	$taxonomies->add( ApprenticeshipOrganization::NAME, new ApprenticeshipOrganization() );
+	$taxonomies->add( UserNationality::NAME, new UserNationality() );
+	$taxonomies->add( UserLanguage::NAME, new UserLanguage() );
+	$taxonomies->add( ApprenticeshipYear::NAME, new ApprenticeshipYear() );
+	$taxonomies->add( LinkDistrictOrganizationApprenticeship::NAME, new LinkDistrictOrganizationApprenticeship() );
+	$taxonomies->add( LinkDistrictOrganizationTrialApprenticeship::NAME, new LinkDistrictOrganizationTrialApprenticeship() );
+	$taxonomies->add( LinkSwissdocOrganizationApprenticeship::NAME, new LinkSwissdocOrganizationApprenticeship() );
+	$taxonomies->add( LinkSwissdocOrganizationTrialApprenticeship::NAME, new LinkSwissdocOrganizationTrialApprenticeship() );
+	$taxonomies->add( OrganizationEmail::NAME, new OrganizationEmail() );
+
+	$district = new District();
+	$taxonomies->add( District::NAME, $district );
+
+	$meta_position = new TermMeta\Position();
+	$meta_position->register();
+	add_action(
+		'admin_init',
+		static function () use ( $district, $meta_position ): void {
+			$meta_position_ui = new Admin\PositionTermUI(
+				$district,
+				$meta_position
+			);
+			$meta_position_ui->register();
+		}
+	);
+
+	$meta_zip = new TermMeta\Zip();
+	$meta_zip->register();
+	add_action(
+		'admin_init',
+		static function () use ( $district, $meta_zip ): void {
+			$meta_zip_ui = new Admin\ZipTermUI(
+				$district,
+				$meta_zip
+			);
+			$meta_zip_ui->register();
+		}
+	);
+
+	$meta_city = new TermMeta\City();
+	$meta_city->register();
+	add_action(
+		'admin_init',
+		static function () use ( $district, $meta_city ): void {
+			$meta_city_ui = new Admin\CityTermUI(
+				$district,
+				$meta_city
+			);
+			$meta_city_ui->register();
+		}
+	);
+
+	$taxonomies->bootstrap();
+}
+
+/**
+ * Registers taxonomies for object types.
+ */
+function register_taxonomy_for_object_types(): void {
+	register_taxonomy_for_object_type( ProfessionField::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionField::NAME, PostType\Event::NAME );
+
+	register_taxonomy_for_object_type( ProfessionInterest::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionSector::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionAlternativeTitle::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionDuration::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionQualification::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( ProfessionBilingualEducation::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( EventSpeaker::NAME, PostType\Event::NAME );
+	register_taxonomy_for_object_type( EventAudience::NAME, PostType\Event::NAME );
+	register_taxonomy_for_object_type( EventTopic::NAME, PostType\Event::NAME );
+	register_taxonomy_for_object_type( EventStatus::NAME, PostType\Event::NAME );
+
+	register_taxonomy_for_object_type( District::NAME, PostType\School::NAME );
+	register_taxonomy_for_object_type( District::NAME, PostType\Office::NAME );
+	register_taxonomy_for_object_type( District::NAME, PostType\Apprenticeship::NAME );
+	register_taxonomy_for_object_type( District::NAME, PostType\TrialApprenticeship::NAME );
+	register_taxonomy_for_object_type( District::NAME, PostType\Event::NAME );
+	register_taxonomy_for_object_type( District::NAME, PostType\Organization::NAME );
+
+	register_taxonomy_for_object_type( Swissdoc::NAME, PostType\Profession::NAME );
+	register_taxonomy_for_object_type( Swissdoc::NAME, PostType\Apprenticeship::NAME );
+	register_taxonomy_for_object_type( Swissdoc::NAME, PostType\TrialApprenticeship::NAME );
+
+	register_taxonomy_for_object_type( ApprenticeshipOrganization::NAME, PostType\Apprenticeship::NAME );
+	register_taxonomy_for_object_type( ApprenticeshipOrganization::NAME, PostType\TrialApprenticeship::NAME );
+	register_taxonomy_for_object_type( ApprenticeshipOrganization::NAME, PostType\Organization::NAME );
+	register_taxonomy_for_object_type( ApprenticeshipOrganization::NAME, PostType\Event::NAME );
+
+	register_taxonomy_for_object_type( LinkDistrictOrganizationApprenticeship::NAME, PostType\Organization::NAME );
+	register_taxonomy_for_object_type( LinkDistrictOrganizationTrialApprenticeship::NAME, PostType\Organization::NAME );
+	register_taxonomy_for_object_type( LinkSwissdocOrganizationApprenticeship::NAME, PostType\Organization::NAME );
+	register_taxonomy_for_object_type( LinkSwissdocOrganizationTrialApprenticeship::NAME, PostType\Organization::NAME );
+
+	register_taxonomy_for_object_type( OrganizationEmail::NAME, PostType\Organization::NAME );
+
+	register_taxonomy_for_object_type( ApprenticeshipYear::NAME, PostType\Apprenticeship::NAME );
+
+	register_taxonomy_for_object_type( UserNationality::NAME, 'user' );
+	register_taxonomy_for_object_type( UserLanguage::NAME, 'user' );
+}
+```
diff --git a/composer.json b/composer.json
index 41a716e..6d4e165 100644
--- a/composer.json
+++ b/composer.json
@@ -34,6 +34,6 @@
     }
   },
   "scripts": {
-    "analyze": "vendor/bin/phpstan analyze --no-progress"
+    "analyze": "vendor/bin/phpstan analyze --no-progress --memory-limit 1G"
   }
 }
diff --git a/inc/Admin/AjaxAction.php b/inc/Admin/AjaxAction.php
index d5671e4..5ae0b51 100644
--- a/inc/Admin/AjaxAction.php
+++ b/inc/Admin/AjaxAction.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common\Admin;
 
 use Required\Common\Contracts\Registrable;
@@ -16,7 +18,7 @@
  */
 abstract class AjaxAction implements Registrable {
 
-	public const ACTION = 'ajax-action';
+	public const string ACTION = 'ajax-action';
 
 	/**
 	 * Whether the Ajax action can be called unauthenticated.
@@ -32,7 +34,7 @@ abstract class AjaxAction implements Registrable {
 	 *
 	 * @param bool $allow Whether the Ajax action can be called unauthenticated.
 	 */
-	public function allow_unauthenticated( bool $allow ) {
+	public function allow_unauthenticated( bool $allow ): void {
 		$this->allow_unauthenticated = $allow;
 	}
 
@@ -41,7 +43,7 @@ public function allow_unauthenticated( bool $allow ) {
 	 *
 	 * @since 0.1.0
 	 */
-	abstract public function callback();
+	abstract public function callback(): void;
 
 	/**
 	 * Registers the action.
diff --git a/inc/Admin/Page.php b/inc/Admin/Page.php
index a4ebb22..21756a6 100644
--- a/inc/Admin/Page.php
+++ b/inc/Admin/Page.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common\Admin;
 
 use Required\Common\Contracts\Registrable;
@@ -22,10 +24,8 @@ class Page implements Registrable {
 	 * @since 0.1.0
 	 *
 	 * @see is_admin()
-	 *
-	 * @var int
 	 */
-	public const ADMIN = 1;
+	public const int ADMIN = 1;
 
 	/**
 	 * Type of admin page.
@@ -33,10 +33,8 @@ class Page implements Registrable {
 	 * @since 0.1.0
 	 *
 	 * @see is_network_admin()
-	 *
-	 * @var int
 	 */
-	public const ADMIN_NETWORK = 2;
+	public const int ADMIN_NETWORK = 2;
 
 	/**
 	 * Type of admin page.
@@ -44,10 +42,8 @@ class Page implements Registrable {
 	 * @since 0.1.0
 	 *
 	 * @see is_user_admin()
-	 *
-	 * @var int
 	 */
-	public const ADMIN_USER = 3;
+	public const int ADMIN_USER = 3;
 
 	/**
 	 * Type of admin screen.
@@ -56,7 +52,7 @@ class Page implements Registrable {
 	 *
 	 * @var int
 	 */
-	private $admin;
+	private int $admin;
 
 	/**
 	 * The text to be displayed in the title tags of the page when the menu is selected.
@@ -65,7 +61,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $title;
+	private string $title;
 
 	/**
 	 * The text to be used for the menu.
@@ -74,7 +70,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $menu_title;
+	private string $menu_title;
 
 	/**
 	 * The capability required for this menu to be displayed to the user.
@@ -83,7 +79,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $capability;
+	private string $capability;
 
 	/**
 	 * The slug name to refer to this menu by (should be unique for this menu).
@@ -92,7 +88,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $menu_slug;
+	private string $menu_slug;
 
 	/**
 	 * The view to render the admin page.
@@ -101,7 +97,7 @@ class Page implements Registrable {
 	 *
 	 * @var \Required\Common\Admin\PageView
 	 */
-	private $view;
+	private PageView $view;
 
 	/**
 	 * The slug name for the parent menu (or the file name of a standard WordPress admin page).
@@ -110,7 +106,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $parent_slug;
+	private string $parent_slug;
 
 	/**
 	 * The icon to be used for the menu.
@@ -119,7 +115,7 @@ class Page implements Registrable {
 	 *
 	 * @var string
 	 */
-	private $icon;
+	private string $icon;
 
 	/**
 	 * The position in the menu order this one should appear.
@@ -128,25 +124,25 @@ class Page implements Registrable {
 	 *
 	 * @var null|int
 	 */
-	private $position;
+	private ?int $position;
 
 	/**
 	 * The page's hook_suffix.
 	 *
 	 * @since 0.1.0
 	 *
-	 * @var string
+	 * @var string|false
 	 */
-	private $hook_name;
+	private string|false $hook_name = false;
 
 	/**
 	 * Callback to be called when page is loaded.
 	 *
 	 * @since 0.1.0
 	 *
-	 * @var string
+	 * @var callable|null
 	 */
-	private $on_load_callback;
+	private $on_load_callback = null;
 
 	/**
 	 * Constructor.
@@ -163,7 +159,7 @@ class Page implements Registrable {
 	 * @param string                          $icon        Optional. The icon to be used for the menu.
 	 * @param null|int                        $position    Optional. The position in the menu order this one should appear.
 	 */
-	public function __construct( int $admin, string $title, string $menu_title, string $capability, string $menu_slug, PageView $view, string $parent_slug = '', string $icon = '', $position = null ) {
+	public function __construct( int $admin, string $title, string $menu_title, string $capability, string $menu_slug, PageView $view, string $parent_slug = '', string $icon = '', ?int $position = null ) {
 		$this->admin       = $admin;
 		$this->title       = $title;
 		$this->menu_title  = $menu_title;
@@ -179,10 +175,8 @@ public function __construct( int $admin, string $title, string $menu_title, stri
 	 * Returns the action for registering the page.
 	 *
 	 * @since 0.1.0
-	 *
-	 * @return string
 	 */
-	private function get_action() {
+	private function get_action(): string {
 		switch ( $this->admin ) {
 			case static::ADMIN:
 				return 'admin_menu';
@@ -203,11 +197,11 @@ private function get_action() {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @return callable Callback for adding the page to the admin menu.
+	 * @return \Closure Callback for adding the page to the admin menu.
 	 */
-	private function get_callback() {
+	private function get_callback(): \Closure {
 		if ( $this->parent_slug ) {
-			return function() {
+			return function (): void {
 				$this->hook_name = add_submenu_page(
 					$this->parent_slug,
 					$this->title,
@@ -217,7 +211,7 @@ private function get_callback() {
 					[ $this->view, 'render' ]
 				);
 
-				if ( $this->hook_name && is_callable( $this->on_load_callback ) ) {
+				if ( $this->hook_name && \is_callable( $this->on_load_callback ) ) {
 					add_action(
 						"load-{$this->hook_name}",
 						$this->on_load_callback
@@ -225,7 +219,7 @@ private function get_callback() {
 				}
 			};
 		} else {
-			return function() {
+			return function (): void {
 				$this->hook_name = add_menu_page(
 					$this->title,
 					$this->menu_title,
@@ -236,7 +230,7 @@ private function get_callback() {
 					$this->position
 				);
 
-				if ( $this->hook_name && is_callable( $this->on_load_callback ) ) {
+				if ( $this->hook_name && \is_callable( $this->on_load_callback ) ) {
 					add_action(
 						"load-{$this->hook_name}",
 						$this->on_load_callback
@@ -251,9 +245,9 @@ private function get_callback() {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @return string The hook name of the menu page.
+	 * @return string|false The hook name of the menu page.
 	 */
-	public function get_hook_name() {
+	public function get_hook_name(): string|false {
 		return $this->hook_name;
 	}
 
@@ -264,7 +258,7 @@ public function get_hook_name() {
 	 *
 	 * @return \Required\Common\Admin\PageView The view of the page.
 	 */
-	public function get_view() {
+	public function get_view(): PageView {
 		return $this->view;
 	}
 
@@ -275,7 +269,7 @@ public function get_view() {
 	 *
 	 * @param callable $callback Callback called when page is loaded.
 	 */
-	public function on_load( callable $callback ) {
+	public function on_load( callable $callback ): void {
 		$this->on_load_callback = $callback;
 	}
 
diff --git a/inc/Admin/PageView.php b/inc/Admin/PageView.php
index 2923d8f..99323e5 100644
--- a/inc/Admin/PageView.php
+++ b/inc/Admin/PageView.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common\Admin;
 
 /**
@@ -19,5 +21,5 @@ interface PageView {
 	 *
 	 * @since 0.1.0
 	 */
-	public function render();
+	public function render(): void;
 }
diff --git a/inc/Admin/PostAction.php b/inc/Admin/PostAction.php
index 15b5c42..0b4c166 100644
--- a/inc/Admin/PostAction.php
+++ b/inc/Admin/PostAction.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common\Admin;
 
 use Required\Common\Contracts\Registrable;
@@ -16,14 +18,14 @@
  */
 abstract class PostAction implements Registrable {
 
-	public const ACTION = 'post-action';
+	public const string ACTION = 'post-action';
 
 	/**
 	 * The callback of the action.
 	 *
 	 * @since 0.1.0
 	 */
-	abstract public function callback();
+	abstract public function callback(): void;
 
 	/**
 	 * Registers the action.
@@ -43,7 +45,7 @@ public function register(): bool {
 	 *
 	 * @return string URL to admin-post.php.
 	 */
-	public static function url() {
+	public static function url(): string {
 		return admin_url( 'admin-post.php?action=' . static::ACTION );
 	}
 }
diff --git a/inc/Container.php b/inc/Container.php
index 6936e5e..a3761e5 100644
--- a/inc/Container.php
+++ b/inc/Container.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common;
 
 use Required\Common\Contracts\Registrable;
@@ -22,9 +24,9 @@ class Container {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @var \Required\Common\Contracts\Registrable[]
+	 * @var array<string,\Required\Common\Contracts\Registrable>
 	 */
-	private $values = [];
+	private array $values = [];
 
 	/**
 	 * Whether this container is $bootstrapped.
@@ -33,18 +35,18 @@ class Container {
 	 *
 	 * @var bool
 	 */
-	private $bootstrapped = false;
+	private bool $bootstrapped = false;
 
 	/**
 	 * Adds a new registrable object to the container.
 	 *
 	 * @since 0.1.0
 	 *
-	 * @param string                                 $name     Name of the registrable object.
-	 * @param \Required\Common\Contracts\Registrable $callable Registrable object.
+	 * @param string                                 $name        Name of the registrable object.
+	 * @param \Required\Common\Contracts\Registrable $registrable Registrable object.
 	 */
-	public function add( $name, Registrable $callable ) {
-		$this->values[ $name ] = $callable;
+	public function add( string $name, Registrable $registrable ): void {
+		$this->values[ $name ] = $registrable;
 	}
 
 	/**
diff --git a/inc/Contracts/PostType.php b/inc/Contracts/PostType.php
index 0875984..e3c53c1 100644
--- a/inc/Contracts/PostType.php
+++ b/inc/Contracts/PostType.php
@@ -13,4 +13,10 @@
  * @since 0.3.2
  */
 interface PostType {
+	/**
+	 * Post type name.
+	 *
+	 * Implementations are expected to override this.
+	 */
+	public const string NAME = '';
 }
diff --git a/inc/Contracts/Registrable.php b/inc/Contracts/Registrable.php
index 9366a4b..0a8709d 100644
--- a/inc/Contracts/Registrable.php
+++ b/inc/Contracts/Registrable.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common\Contracts;
 
 /**
diff --git a/inc/Contracts/ShortcodeView.php b/inc/Contracts/ShortcodeView.php
deleted file mode 100644
index c7c2e02..0000000
--- a/inc/Contracts/ShortcodeView.php
+++ /dev/null
@@ -1,28 +0,0 @@
-<?php
-/**
- * ShortcodeView class.
- *
- * @since 0.1.0
- */
-
-namespace Required\Common\Contracts;
-
-/**
- * Class used to implement shortcode view.
- *
- * @since 0.1.0
- */
-interface ShortcodeView {
-
-	/**
-	 * Renders the shortcode.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param array  $attributes    Attributes of the shortcode.
-	 * @param null   $content       The content.
-	 * @param string $shortcode_tag The shortcode tag.
-	 * @return string HTML output of the shortcode.
-	 */
-	public function render( $attributes, $content, $shortcode_tag ): string;
-}
diff --git a/inc/Contracts/Taxonomy.php b/inc/Contracts/Taxonomy.php
index 7d587d1..d83765c 100644
--- a/inc/Contracts/Taxonomy.php
+++ b/inc/Contracts/Taxonomy.php
@@ -13,4 +13,10 @@
  * @since 0.3.2
  */
 interface Taxonomy {
+	/**
+	 * Taxonomy name.
+	 *
+	 * Implementations are expected to override this.
+	 */
+	public const string NAME = '';
 }
diff --git a/inc/Legacy/PostMeta.php b/inc/Legacy/PostMeta.php
deleted file mode 100644
index b5727ad..0000000
--- a/inc/Legacy/PostMeta.php
+++ /dev/null
@@ -1,167 +0,0 @@
-<?php
-/**
- * PostMeta class
- *
- * Deprecated: Use Required\Common\PostMeta instead.
- *
- * @since 0.3.1
- */
-
-namespace Required\Common\Legacy;
-
-use Required\Common\Contracts\PostMeta as PostMetaInterface;
-use Required\Common\Contracts\Registrable;
-
-/**
- * Class used to implement post meta.
- *
- * @since 0.1.0
- */
-abstract class PostMeta implements Registrable, PostMetaInterface {
-
-	/**
-	 * Post meta key.
-	 */
-	public const KEY = null;
-
-	/**
-	 * Registers the object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the post meta was registered successfully.
-	 */
-	public function register(): bool {
-		return register_post_meta(
-			$this->post_type(),
-			static::KEY,
-			$this->get_args()
-		);
-	}
-
-	/**
-	 * Gets post meta arguments for this post meta object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @see register_meta() For the supported arguments.
-	 *
-	 * @return array Post meta arguments.
-	 */
-	protected function get_args(): array {
-		return [
-			'type'              => $this->type(),
-			'description'       => $this->description(),
-			'single'            => $this->is_single(),
-			'default'           => $this->default(),
-			'sanitize_callback' => [ $this, 'sanitize' ],
-			'auth_callback'     => [ $this, 'auth' ],
-			'show_in_rest'      => $this->show_in_rest(),
-		];
-	}
-
-	/**
-	 * The post type to register a meta key for.
-	 *
-	 * Pass an empty string to register the meta key across all existing post types.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Post type to register a meta key for.
-	 */
-	protected function post_type(): string {
-		return '';
-	}
-
-	/**
-	 * The type of data associated with this meta key.
-	 *
-	 * Valid values are 'string', 'boolean', 'integer', 'number', 'array', and 'object'.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Type of the data.
-	 */
-	protected function type(): string {
-		return 'string';
-	}
-
-	/**
-	 * A description of the data attached to this meta key.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Description of the data.
-	 */
-	protected function description(): string {
-		return '';
-	}
-
-	/**
-	 * Whether the meta key has one value per object, or an array of values per object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the meta key has one value per object.
-	 */
-	protected function is_single(): bool {
-		return false;
-	}
-
-	/**
-	 * The default value if no value has been set yet.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return mixed The default value.
-	 */
-	protected function default() {
-		return '';
-	}
-
-	/**
-	 * Sanitization of the post meta data.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param mixed  $meta_value      Meta value to sanitize.
-	 * @param string $meta_key        Meta key.
-	 * @param string $object_type     Object type.
-	 * @return mixed Sanitized meta value.
-	 */
-	public function sanitize( $meta_value, $meta_key, $object_type ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
-		return $meta_value;
-	}
-
-	/**
-	 * Whether the user is allowed to edit meta.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param bool   $allowed   Whether the user can add the post meta. Default false.
-	 * @param string $meta_key  The meta key.
-	 * @param int    $object_id Object ID.
-	 * @param int    $user_id   User ID.
-	 * @param string $cap       Capability name.
-	 * @param array  $caps      User capabilities.
-	 * @return bool False if the key is protected, true otherwise.
-	 */
-	public function auth( $allowed, $meta_key, $object_id, $user_id, $cap, $caps ): bool { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
-		return ! is_protected_meta( $meta_key, 'post' );
-	}
-
-	/**
-	 * Whether data associated with this meta key can be considered public and
-	 * should be accessible via the REST API.
-	 *
-	 * When registering complex meta values this argument may optionally be an
-	 * array with 'schema' or 'prepare_callback' keys instead of a boolean.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool|array Whether the data is public.
-	 */
-	protected function show_in_rest() {
-		return false;
-	}
-}
diff --git a/inc/Legacy/PostType.php b/inc/Legacy/PostType.php
deleted file mode 100644
index 0a13eab..0000000
--- a/inc/Legacy/PostType.php
+++ /dev/null
@@ -1,51 +0,0 @@
-<?php
-/**
- * PostType class
- *
- * Deprecated: Use Required\Common\PostType instead.
- *
- * @since 0.3.1
- */
-
-namespace Required\Common\Legacy;
-
-use Required\Common\Contracts\PostType as PostTypeInterface;
-use Required\Common\Contracts\Registrable;
-
-/**
- * Class used to implement custom post types.
- *
- * @since 0.1.0
- */
-abstract class PostType implements Registrable, PostTypeInterface {
-
-	public const NAME = 'post';
-
-	/**
-	 * Creates a post type object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the post type was registered successfully.
-	 */
-	public function register(): bool {
-		if ( ! post_type_exists( static::NAME ) ) {
-			$post_type = register_post_type(
-				static::NAME,
-				$this->get_args()
-			);
-			return ! is_wp_error( $post_type );
-		}
-
-		return true;
-	}
-
-	/**
-	 * Gets post type arguments for this post type object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return array Post type arguments.
-	 */
-	abstract protected function get_args(): array;
-}
diff --git a/inc/Legacy/Taxonomy.php b/inc/Legacy/Taxonomy.php
deleted file mode 100644
index e5601aa..0000000
--- a/inc/Legacy/Taxonomy.php
+++ /dev/null
@@ -1,83 +0,0 @@
-<?php
-/**
- * Taxonomy class
- *
- * Deprecated: Use Required\Common\Taxonomy instead.
- *
- * @since 0.3.1
- */
-
-namespace Required\Common\Legacy;
-
-use Required\Common\Contracts\Registrable;
-use Required\Common\Contracts\Taxonomy as TaxonomyInterface;
-
-/**
- * Class used to implement custom taxonomies.
- *
- * @since 0.1.0
- */
-abstract class Taxonomy implements Registrable, TaxonomyInterface {
-
-	public const NAME = 'category';
-
-	/**
-	 * Object types the taxonomy is associated with.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @var array
-	 */
-	protected $object_types;
-
-	/**
-	 * Creates a taxonomy object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the taxonomy was registered successfully.
-	 */
-	public function register(): bool {
-		if ( ! taxonomy_exists( static::NAME ) ) {
-			$taxonomy = register_taxonomy(
-				static::NAME,
-				$this->get_object_types(),
-				$this->get_args()
-			);
-			return ! is_wp_error( $taxonomy );
-		}
-
-		return true;
-	}
-
-	/**
-	 * Sets object types the taxonomy is associated with.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param array|string $object_type Object type or array of object types with which the taxonomy should be associated.
-	 */
-	public function set_object_types( $object_type ) {
-		$this->object_types = (array) $object_type;
-	}
-
-	/**
-	 * Gets object types the taxonomy is associated with.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return array Object types the taxonomy is associated with.
-	 */
-	public function get_object_types() {
-		return $this->object_types;
-	}
-
-	/**
-	 * Gets taxonomy arguments for this taxonomy object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return array Taxonomy arguments.
-	 */
-	abstract protected function get_args();
-}
diff --git a/inc/Legacy/TermMeta.php b/inc/Legacy/TermMeta.php
deleted file mode 100644
index d9021e8..0000000
--- a/inc/Legacy/TermMeta.php
+++ /dev/null
@@ -1,167 +0,0 @@
-<?php
-/**
- * TermMeta class
- *
- * Deprecated: Use Required\Common\TermMeta instead.
- *
- * @since 0.3.1
- */
-
-namespace Required\Common\Legacy;
-
-use Required\Common\Contracts\Registrable;
-use Required\Common\Contracts\TermMeta as TermMetaInterface;
-
-/**
- * Class used to implement term meta.
- *
- * @since 0.1.0
- */
-abstract class TermMeta implements Registrable, TermMetaInterface {
-
-	/**
-	 * Term meta key.
-	 */
-	public const KEY = null;
-
-	/**
-	 * Registers the object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the term meta was registered successfully.
-	 */
-	public function register(): bool {
-		return register_term_meta(
-			$this->taxonomy(),
-			static::KEY,
-			$this->get_args()
-		);
-	}
-
-	/**
-	 * Gets term meta arguments for this term meta object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @see register_meta() For the supported arguments.
-	 *
-	 * @return array Term meta arguments.
-	 */
-	protected function get_args(): array {
-		return [
-			'type'              => $this->type(),
-			'description'       => $this->description(),
-			'single'            => $this->is_single(),
-			'default'           => $this->default(),
-			'sanitize_callback' => [ $this, 'sanitize' ],
-			'auth_callback'     => [ $this, 'auth' ],
-			'show_in_rest'      => $this->show_in_rest(),
-		];
-	}
-
-	/**
-	 * The taxonomy to register a meta key for.
-	 *
-	 * Pass an empty string to register the meta key across all existing taxonomies.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Taxonomy to register a meta key for.
-	 */
-	protected function taxonomy(): string {
-		return '';
-	}
-
-	/**
-	 * The type of data associated with this meta key.
-	 *
-	 * Valid values are 'string', 'boolean', 'integer', 'number', 'array', and 'object'.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Type of the data.
-	 */
-	protected function type(): string {
-		return 'string';
-	}
-
-	/**
-	 * A description of the data attached to this meta key.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return string Description of the data.
-	 */
-	protected function description(): string {
-		return '';
-	}
-
-	/**
-	 * Whether the meta key has one value per object, or an array of values per object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether the meta key has one value per object.
-	 */
-	protected function is_single(): bool {
-		return false;
-	}
-
-	/**
-	 * The default value if no value has been set yet.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return mixed The default value.
-	 */
-	protected function default() {
-		return '';
-	}
-
-	/**
-	 * Sanitization of the term meta data.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param mixed  $meta_value      Meta value to sanitize.
-	 * @param string $meta_key        Meta key.
-	 * @param string $object_type     Object type.
-	 * @return mixed Sanitized meta value.
-	 */
-	public function sanitize( $meta_value, $meta_key, $object_type ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
-		return $meta_value;
-	}
-
-	/**
-	 * Whether the user is allowed to edit meta.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param bool   $allowed   Whether the user can add the term meta. Default false.
-	 * @param string $meta_key  The meta key.
-	 * @param int    $object_id Object ID.
-	 * @param int    $user_id   User ID.
-	 * @param string $cap       Capability name.
-	 * @param array  $caps      User capabilities.
-	 * @return bool False if the key is protected, true otherwise.
-	 */
-	public function auth( $allowed, $meta_key, $object_id, $user_id, $cap, $caps ): bool { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
-		return ! is_protected_meta( $meta_key, 'term' );
-	}
-
-	/**
-	 * Whether data associated with this meta key can be considered public and
-	 * should be accessible via the REST API.
-	 *
-	 * When registering complex meta values this argument may optionally be an
-	 * array with 'schema' or 'prepare_callback' keys instead of a boolean.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool|array Whether the data is public.
-	 */
-	protected function show_in_rest() {
-		return false;
-	}
-}
diff --git a/inc/PostMeta.php b/inc/PostMeta.php
index 25ae138..bc08451 100644
--- a/inc/PostMeta.php
+++ b/inc/PostMeta.php
@@ -23,7 +23,7 @@ abstract class PostMeta implements Registrable, PostMetaInterface {
 	/**
 	 * Post meta key.
 	 */
-	public const KEY = null;
+	public const string KEY = '';
 
 	/**
 	 * Registers the object.
@@ -33,10 +33,30 @@ abstract class PostMeta implements Registrable, PostMetaInterface {
 	 * @return bool Whether the post meta was registered successfully.
 	 */
 	public function register(): bool {
+		if ( static::KEY === '' ) {
+			return false;
+		}
+
+		/**
+		 * @phpstan-var array{
+		 *   object_subtype?: string,
+		 *   type?: string,
+		 *   label?: string,
+		 *   description?: string,
+		 *   single?: bool,
+		 *   default?: mixed,
+		 *   sanitize_callback?: callable,
+		 *   auth_callback?: callable,
+		 *   show_in_rest?: bool|array<string, mixed>,
+		 *   revisions_enabled?: bool,
+		 * } $args
+		 */
+		$args = $this->get_args()->toArray();
+
 		return register_post_meta(
 			$this->post_type(),
 			static::KEY,
-			$this->get_args()->toArray()
+			$args
 		);
 	}
 
@@ -57,7 +77,7 @@ protected function get_args(): PostMetaArgs {
 		$args->single            = $this->is_single();
 		$args->default           = $this->default();
 		$args->sanitize_callback = [ $this, 'sanitize' ];
-		$args->auth_callback     = [ $this, 'auth' ];
+		$args->auth_callback     = [ $this, 'auth_callback' ];
 		$args->show_in_rest      = $this->show_in_rest();
 
 		return $args;
@@ -83,7 +103,7 @@ protected function post_type(): string {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @return string Type of the data.
+	 * @return 'array'|'boolean'|'integer'|'number'|'object'|'string' Type of the data.
 	 */
 	protected function type(): string {
 		return PostMetaArgs::TYPE_STRING;
@@ -118,7 +138,7 @@ protected function is_single(): bool {
 	 *
 	 * @return mixed The default value.
 	 */
-	protected function default() {
+	protected function default(): mixed {
 		return '';
 	}
 
@@ -132,7 +152,7 @@ protected function default() {
 	 * @param string $object_type     Object type.
 	 * @return mixed Sanitized meta value.
 	 */
-	public function sanitize( $meta_value, string $meta_key, string $object_type ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+	public function sanitize( mixed $meta_value, string $meta_key, string $object_type ): mixed { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
 		return $meta_value;
 	}
 
@@ -153,6 +173,21 @@ public function auth( bool $allowed, string $meta_key, int $object_id, int $user
 		return ! is_protected_meta( $meta_key, 'post' );
 	}
 
+	/**
+	 * Adapter for the narrower `johnbillion/args` auth callback signature.
+	 *
+	 * @since 0.1.0
+	 *
+	 * @param bool   $allowed        Whether the user can add the post meta.
+	 * @param string $meta_key       The meta key.
+	 * @param string $object_type    Object type.
+	 * @param string $object_subtype Object subtype.
+	 * @return bool Whether the user is allowed to edit meta.
+	 */
+	public function auth_callback( bool $allowed, string $meta_key, string $object_type, string $object_subtype = '' ): bool { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		return $this->auth( $allowed, $meta_key, 0, 0, '', [] );
+	}
+
 	/**
 	 * Whether data associated with this meta key can be considered public and
 	 * should be accessible via the REST API.
@@ -163,11 +198,11 @@ public function auth( bool $allowed, string $meta_key, int $object_id, int $user
 	 * @since 0.1.0
 	 *
 	 * @return bool|array{
-	 *     schema: mixed[],
-	 *     prepare_callback: callable(mixed,\WP_REST_Request,mixed[]): mixed,
+	 *     schema: array<string, mixed>,
+	 *     prepare_callback: callable(mixed,\WP_REST_Request<array<string, mixed>>,array<string, mixed>): mixed,
 	 * }
 	 */
-	protected function show_in_rest() {
+	protected function show_in_rest(): array|bool {
 		return false;
 	}
 }
diff --git a/inc/PostType.php b/inc/PostType.php
index 1860fb6..e473519 100644
--- a/inc/PostType.php
+++ b/inc/PostType.php
@@ -20,7 +20,7 @@
  */
 abstract class PostType implements Registrable, PostTypeInterface {
 
-	public const NAME = 'post';
+	public const string NAME = 'post';
 
 	/**
 	 * Creates a post type object.
@@ -30,10 +30,57 @@ abstract class PostType implements Registrable, PostTypeInterface {
 	 * @return bool Whether the post type was registered successfully.
 	 */
 	public function register(): bool {
-		if ( ! post_type_exists( static::NAME ) ) {
+		/** @var lowercase-string&non-empty-string $name */
+		$name = static::NAME;
+
+		if ( ! post_type_exists( $name ) ) {
+			/**
+			 * WordPress stubs currently treat this as an array shape. `johnbillion/args`
+			 * returns a plain `array<string, mixed>`, so we assert the expected shape here.
+			 *
+			 * @phpstan-var array{
+			 *   label?: string,
+			 *   labels?: string[],
+			 *   description?: string,
+			 *   public?: bool,
+			 *   hierarchical?: bool,
+			 *   exclude_from_search?: bool,
+			 *   publicly_queryable?: bool,
+			 *   show_ui?: bool,
+			 *   show_in_menu?: bool|string,
+			 *   show_in_nav_menus?: bool,
+			 *   show_in_admin_bar?: bool,
+			 *   show_in_rest?: bool,
+			 *   rest_base?: string,
+			 *   rest_namespace?: string,
+			 *   rest_controller_class?: string,
+			 *   autosave_rest_controller_class?: string|bool,
+			 *   revisions_rest_controller_class?: string|bool,
+			 *   late_route_registration?: bool,
+			 *   menu_position?: int,
+			 *   menu_icon?: string,
+			 *   capability_type?: string|array<int, string>,
+			 *   capabilities?: string[],
+			 *   map_meta_cap?: bool,
+			 *   supports?: array<int, mixed>|false,
+			 *   register_meta_box_cb?: callable,
+			 *   taxonomies?: string[],
+			 *   has_archive?: bool|string,
+			 *   rewrite?: bool|array{slug?: string, with_front?: bool, feeds?: bool, pages?: bool, ep_mask?: int},
+			 *   query_var?: string|bool,
+			 *   can_export?: bool,
+			 *   delete_with_user?: bool,
+			 *   template?: array<int, mixed>,
+			 *   template_lock?: string|false,
+			 *   _builtin?: bool,
+			 *   _edit_link?: string,
+			 * } $args
+			 */
+			$args = $this->get_args()->toArray();
+
 			$post_type = register_post_type(
-				static::NAME,
-				$this->get_args()->toArray()
+				$name,
+				$args
 			);
 			return ! is_wp_error( $post_type );
 		}
diff --git a/inc/Shortcode.php b/inc/Shortcode.php
deleted file mode 100644
index bb2a6f8..0000000
--- a/inc/Shortcode.php
+++ /dev/null
@@ -1,55 +0,0 @@
-<?php
-/**
- * Shortcode class
- *
- * @since 0.1.0
- */
-
-namespace Required\Common;
-
-use Required\Common\Contracts\Registrable;
-
-/**
- * Class used to implement shortcode.
- *
- * @since 0.1.0
- */
-abstract class Shortcode implements Registrable {
-
-	public const TAG = 'shortcode';
-
-	/**
-	 * Shortcode view object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @var \Required\Common\Contracts\ShortcodeView
-	 */
-	protected $view;
-
-	/**
-	 * Creates a shortcode object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @param \Required\Common\Contracts\ShortcodeView $view Shortcode View.
-	 */
-	public function __construct( $view ) {
-		$this->view = $view;
-	}
-
-	/**
-	 * Creates a shortcode object.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @return bool Whether shortcode was registered successfully.
-	 */
-	public function register(): bool {
-		add_shortcode(
-			static::TAG,
-			[ $this->view, 'render' ]
-		);
-		return shortcode_exists( static::TAG );
-	}
-}
diff --git a/inc/Taxonomy.php b/inc/Taxonomy.php
index 077ddfe..689b176 100644
--- a/inc/Taxonomy.php
+++ b/inc/Taxonomy.php
@@ -20,16 +20,10 @@
  */
 abstract class Taxonomy implements Registrable, TaxonomyInterface {
 
-	public const NAME = 'category';
+	public const string NAME = 'category';
 
-	/**
-	 * Object types the taxonomy is associated with.
-	 *
-	 * @since 0.1.0
-	 *
-	 * @var array
-	 */
-	protected $object_types = [];
+	/** @var array<string> */
+	protected array $object_types = [];
 
 	/**
 	 * Creates a taxonomy object.
@@ -39,11 +33,47 @@ abstract class Taxonomy implements Registrable, TaxonomyInterface {
 	 * @return bool Whether the taxonomy was registered successfully.
 	 */
 	public function register(): bool {
-		if ( ! taxonomy_exists( static::NAME ) ) {
+		$name = static::NAME;
+
+		if ( ! taxonomy_exists( $name ) ) {
+			/**
+			 * WordPress stubs currently treat this as an array shape. `johnbillion/args`
+			 * returns a plain `array<string, mixed>`, so we assert the expected shape here.
+			 *
+			 * @phpstan-var array{
+			 *   labels?: string[],
+			 *   description?: string,
+			 *   public?: bool,
+			 *   publicly_queryable?: bool,
+			 *   hierarchical?: bool,
+			 *   show_ui?: bool,
+			 *   show_in_menu?: bool,
+			 *   show_in_nav_menus?: bool,
+			 *   show_in_rest?: bool,
+			 *   rest_base?: string,
+			 *   rest_namespace?: string,
+			 *   rest_controller_class?: string,
+			 *   show_tagcloud?: bool,
+			 *   show_in_quick_edit?: bool,
+			 *   show_admin_column?: bool,
+			 *   meta_box_cb?: bool|callable,
+			 *   meta_box_sanitize_cb?: callable,
+			 *   capabilities?: array{manage_terms?: string, edit_terms?: string, delete_terms?: string, assign_terms?: string},
+			 *   rewrite?: bool|array{slug?: string, with_front?: bool, hierarchical?: bool, ep_mask?: int},
+			 *   query_var?: string|bool,
+			 *   update_count_callback?: callable,
+			 *   default_term?: string|array{name?: string, slug?: string, description?: string},
+			 *   sort?: bool,
+			 *   args?: array<string, mixed>,
+			 *   _builtin?: bool,
+			 * } $args
+			 */
+			$args = $this->get_args()->toArray();
+
 			$taxonomy = register_taxonomy(
-				static::NAME,
+				$name,
 				$this->get_object_types(),
-				$this->get_args()->toArray()
+				$args
 			);
 			return ! is_wp_error( $taxonomy );
 		}
@@ -58,8 +88,8 @@ public function register(): bool {
 	 *
 	 * @param string[]|string $object_type Object type or array of object types with which the taxonomy should be associated.
 	 */
-	public function set_object_types( $object_type ): void {
-		$this->object_types = (array) $object_type;
+	public function set_object_types( array|string $object_type ): void {
+		$this->object_types = array_map( 'strval', (array) $object_type );
 	}
 
 	/**
diff --git a/inc/TermMeta.php b/inc/TermMeta.php
index 15b5a4f..89d71a4 100644
--- a/inc/TermMeta.php
+++ b/inc/TermMeta.php
@@ -23,7 +23,7 @@ abstract class TermMeta implements Registrable, TermMetaInterface {
 	/**
 	 * Term meta key.
 	 */
-	public const KEY = null;
+	public const string KEY = '';
 
 	/**
 	 * Registers the object.
@@ -33,10 +33,30 @@ abstract class TermMeta implements Registrable, TermMetaInterface {
 	 * @return bool Whether the term meta was registered successfully.
 	 */
 	public function register(): bool {
+		if ( static::KEY === '' ) {
+			return false;
+		}
+
+		/**
+		 * @phpstan-var array{
+		 *   object_subtype?: string,
+		 *   type?: string,
+		 *   label?: string,
+		 *   description?: string,
+		 *   single?: bool,
+		 *   default?: mixed,
+		 *   sanitize_callback?: callable,
+		 *   auth_callback?: callable,
+		 *   show_in_rest?: bool|array<string, mixed>,
+		 *   revisions_enabled?: bool,
+		 * } $args
+		 */
+		$args = $this->get_args()->toArray();
+
 		return register_term_meta(
 			$this->taxonomy(),
 			static::KEY,
-			$this->get_args()->toArray()
+			$args
 		);
 	}
 
@@ -57,7 +77,7 @@ protected function get_args(): TermMetaArgs {
 		$args->single            = $this->is_single();
 		$args->default           = $this->default();
 		$args->sanitize_callback = [ $this, 'sanitize' ];
-		$args->auth_callback     = [ $this, 'auth' ];
+		$args->auth_callback     = [ $this, 'auth_callback' ];
 		$args->show_in_rest      = $this->show_in_rest();
 
 		return $args;
@@ -83,7 +103,7 @@ protected function taxonomy(): string {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @return string Type of the data.
+	 * @return 'array'|'boolean'|'integer'|'number'|'object'|'string' Type of the data.
 	 */
 	protected function type(): string {
 		return TermMetaArgs::TYPE_STRING;
@@ -118,7 +138,7 @@ protected function is_single(): bool {
 	 *
 	 * @return mixed The default value.
 	 */
-	protected function default() {
+	protected function default(): mixed {
 		return '';
 	}
 
@@ -132,7 +152,7 @@ protected function default() {
 	 * @param string $object_type     Object type.
 	 * @return mixed Sanitized meta value.
 	 */
-	public function sanitize( $meta_value, string $meta_key, string $object_type ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+	public function sanitize( mixed $meta_value, string $meta_key, string $object_type ): mixed { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
 		return $meta_value;
 	}
 
@@ -153,6 +173,21 @@ public function auth( bool $allowed, string $meta_key, int $object_id, int $user
 		return ! is_protected_meta( $meta_key, 'term' );
 	}
 
+	/**
+	 * Adapter for the narrower `johnbillion/args` auth callback signature.
+	 *
+	 * @since 0.1.0
+	 *
+	 * @param bool   $allowed        Whether the user can add the term meta.
+	 * @param string $meta_key       The meta key.
+	 * @param string $object_type    Object type.
+	 * @param string $object_subtype Object subtype.
+	 * @return bool Whether the user is allowed to edit meta.
+	 */
+	public function auth_callback( bool $allowed, string $meta_key, string $object_type, string $object_subtype = '' ): bool { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		return $this->auth( $allowed, $meta_key, 0, 0, '', [] );
+	}
+
 	/**
 	 * Whether data associated with this meta key can be considered public and
 	 * should be accessible via the REST API.
@@ -163,11 +198,11 @@ public function auth( bool $allowed, string $meta_key, int $object_id, int $user
 	 * @since 0.1.0
 	 *
 	 * @return bool|array{
-	 *     schema: mixed[],
-	 *     prepare_callback: callable(mixed,\WP_REST_Request,mixed[]): mixed,
+	 *     schema: array<string, mixed>,
+	 *     prepare_callback: callable(mixed,\WP_REST_Request<array<string, mixed>>,array<string, mixed>): mixed,
 	 * }
 	 */
-	protected function show_in_rest() {
+	protected function show_in_rest(): array|bool {
 		return false;
 	}
 }
diff --git a/inc/TermMetaAdminUI.php b/inc/TermMetaAdminUI.php
index e3bd628..4fc3b68 100644
--- a/inc/TermMetaAdminUI.php
+++ b/inc/TermMetaAdminUI.php
@@ -5,6 +5,8 @@
  * @since 0.1.0
  */
 
+declare( strict_types=1 );
+
 namespace Required\Common;
 
 use Required\Common\Contracts\Registrable;
@@ -24,14 +26,14 @@ abstract class TermMetaAdminUI implements Registrable {
 	 *
 	 * @var \Required\Common\Contracts\Taxonomy
 	 */
-	protected $taxonomy;
+	protected Taxonomy $taxonomy;
 
 	/**
 	 * The term meta.
 	 *
 	 * @var \Required\Common\Contracts\TermMeta
 	 */
-	protected $term_meta;
+	protected TermMeta $term_meta;
 
 	/**
 	 * Constructor.
@@ -67,7 +69,7 @@ public function register(): bool {
 		// List table.
 		add_filter( "manage_edit-{$taxonomy}_columns", [ $this, 'add_column' ] );
 		add_filter( "manage_edit-{$taxonomy}_sortable_columns", [ $this, 'add_sortable_column' ] );
-		add_action( "manage_edit-{$taxonomy}_custom_column", [ $this, 'render_column' ] );
+		add_filter( "manage_{$taxonomy}_custom_column", [ $this, 'render_column' ], 10, 3 );
 
 		return true;
 	}
@@ -79,7 +81,7 @@ public function register(): bool {
 	 *
 	 * @param int $term_id Term ID.
 	 */
-	abstract public function add( int $term_id );
+	abstract public function add( int $term_id ): void;
 
 	/**
 	 * Updates an existing term meta.
@@ -88,14 +90,14 @@ abstract public function add( int $term_id );
 	 *
 	 * @param int $term_id Term ID.
 	 */
-	abstract public function update( int $term_id );
+	abstract public function update( int $term_id ): void;
 
 	/**
 	 * Renders field when adding a new term.
 	 *
 	 * @since 0.1.0
 	 */
-	abstract public function render_add_field();
+	abstract public function render_add_field(): void;
 
 	/**
 	 * Renders field when editing a term.
@@ -104,15 +106,15 @@ abstract public function render_add_field();
 	 *
 	 * @param \WP_Term $term Current term object.
 	 */
-	abstract public function render_edit_field( WP_Term $term );
+	abstract public function render_edit_field( WP_Term $term ): void;
 
 	/**
 	 * Adds the term meta to the list of list table columns.
 	 *
 	 * @since 0.1.0
 	 *
-	 * @param array $columns An array of columns.
-	 * @return array An array of columns.
+	 * @param array<string, string> $columns An array of columns.
+	 * @return array<string, string> An array of columns.
 	 */
 	public function add_column( array $columns ): array {
 		return $columns;
@@ -123,8 +125,8 @@ public function add_column( array $columns ): array {
 	 *
 	 * @since 0.1.0
 	 *
-	 * @param array $sortable_columns An array of sortable columns.
-	 * @return array An array of sortable columns.
+	 * @param array<string, string> $sortable_columns An array of sortable columns.
+	 * @return array<string, string> An array of sortable columns.
 	 */
 	public function add_sortable_column( array $sortable_columns ): array {
 		return $sortable_columns;
@@ -135,8 +137,12 @@ public function add_sortable_column( array $sortable_columns ): array {
 	 *
 	 * @since 0.1.0
 	 *
+	 * @param string $output      Custom column output. Default empty.
 	 * @param string $column_name Name of the column.
 	 * @param int    $term_id     Term ID.
+	 * @return string The column output.
 	 */
-	public function render_column( string $column_name, int $term_id ) {} // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+	public function render_column( string $output, string $column_name, int $term_id ): string { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		return $output;
+	}
 }
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 91b7fb8..db6ba7c 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -4,7 +4,9 @@
 
 	<file>.</file>
 
-	<rule ref="Required"/>
+	<rule ref="Required">
+		<exclude name="Squiz.Commenting.VariableComment.MissingVar"/>
+	</rule>
 
 	<!-- The minimum supported WordPress version for all sniffs which use it. -->
 	<config name="minimum_supported_wp_version" value="6.8"/>
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 99f3173..04ebabf 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -4,4 +4,4 @@ parameters:
     level: max
     inferPrivatePropertyTypeFromConstructor: true
     paths:
-        - src/
+        - inc/