diff --git src/wp-includes/class-wp-customize-control.php src/wp-includes/class-wp-customize-control.php
index 07c6dcfce1..267989da5e 100644
--- src/wp-includes/class-wp-customize-control.php
+++ src/wp-includes/class-wp-customize-control.php
@@ -37,12 +37,18 @@ class WP_Customize_Control {
 	public $instance_number;
 
 	/**
+	 * Customizer manager.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var WP_Customize_Manager
 	 */
 	public $manager;
 
 	/**
+	 * Control ID.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
@@ -51,6 +57,7 @@ class WP_Customize_Control {
 	/**
 	 * All settings tied to the control.
 	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var array
 	 */
@@ -59,6 +66,7 @@ class WP_Customize_Control {
 	/**
 	 * The primary setting for the control (if there is one).
 	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
@@ -77,38 +85,56 @@ class WP_Customize_Control {
 	public $capability;
 
 	/**
+	 * Order priority to load the control in Customizer.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var int
 	 */
 	public $priority = 10;
 
 	/**
+	 * Section the control belongs to.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
 	public $section = '';
 
 	/**
+	 * Label for the control.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
 	public $label = '';
 
 	/**
+	 * Description for the control.
+	 *
+	 * @since 4.0.0
 	 * @access public
 	 * @var string
 	 */
 	public $description = '';
 
 	/**
-	 * @todo: Remove choices
+	 * List of choices for 'radio' or 'select' type controls, where values are the keys, and labels are the values.
 	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var array
 	 */
 	public $choices = array();
 
 	/**
+	 * List of custom input attributes for control output, where attribute names are the keys and values are the values.
+	 *
+	 * Not used for 'checkbox', 'radio', 'select', 'textarea', or 'dropdown-pages' control types.
+	 *
+	 * @since 4.0.0
 	 * @access public
 	 * @var array
 	 */
@@ -125,12 +151,16 @@ class WP_Customize_Control {
 
 	/**
 	 * @deprecated It is better to just call the json() method
+	 * @since 3.4.0
 	 * @access public
 	 * @var array
 	 */
 	public $json = array();
 
 	/**
+	 * Control's Type.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
@@ -235,7 +265,6 @@ class WP_Customize_Control {
 	 * Check whether control is active to current Customizer preview.
 	 *
 	 * @since 4.0.0
-	 * @access public
 	 *
 	 * @return bool Whether the control is active to the current preview.
 	 */
@@ -263,7 +292,6 @@ class WP_Customize_Control {
 	 * provide an 'active_callback' argument to the constructor.
 	 *
 	 * @since 4.0.0
-	 * @access public
 	 *
 	 * @return true Always true.
 	 */
@@ -446,7 +474,6 @@ class WP_Customize_Control {
 	 * Render the custom attributes for the control's input element.
 	 *
 	 * @since 4.0.0
-	 * @access public
 	 */
 	public function input_attrs() {
 		foreach ( $this->input_attrs as $attr => $value ) {
@@ -648,56 +675,92 @@ class WP_Customize_Control {
 
 }
 
-/** WP_Customize_Color_Control class */
+/**
+ * WP_Customize_Color_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-color-control.php' );
 
-/** WP_Customize_Media_Control class */
+/**
+ * WP_Customize_Media_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-media-control.php' );
 
-/** WP_Customize_Upload_Control class */
+/**
+ * WP_Customize_Upload_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-upload-control.php' );
 
-/** WP_Customize_Image_Control class */
+/**
+ * WP_Customize_Image_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-image-control.php' );
 
-/** WP_Customize_Background_Image_Control class */
+/**
+ * WP_Customize_Background_Image_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-background-image-control.php' );
 
-/** WP_Customize_Background_Position_Control class */
+/**
+ * WP_Customize_Background_Position_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-background-position-control.php' );
 
-/** WP_Customize_Cropped_Image_Control class */
+/**
+ * WP_Customize_Cropped_Image_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-cropped-image-control.php' );
 
-/** WP_Customize_Site_Icon_Control class */
+/**
+ * WP_Customize_Site_Icon_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-site-icon-control.php' );
 
-/** WP_Customize_Header_Image_Control class */
+/**
+ * WP_Customize_Header_Image_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-header-image-control.php' );
 
-/** WP_Customize_Theme_Control class */
+/**
+ * WP_Customize_Theme_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-theme-control.php' );
 
-/** WP_Widget_Area_Customize_Control class */
+/**
+ * WP_Widget_Area_Customize_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-widget-area-customize-control.php' );
 
-/** WP_Widget_Form_Customize_Control class */
+/**
+ * WP_Widget_Form_Customize_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-widget-form-customize-control.php' );
 
-/** WP_Customize_Nav_Menu_Control class */
+/**
+ * WP_Customize_Nav_Menu_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-control.php' );
 
-/** WP_Customize_Nav_Menu_Item_Control class */
+/**
+ * WP_Customize_Nav_Menu_Item_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-item-control.php' );
 
-/** WP_Customize_Nav_Menu_Location_Control class */
+/**
+ * WP_Customize_Nav_Menu_Location_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-location-control.php' );
 
-/** WP_Customize_Nav_Menu_Name_Control class */
+/**
+ * WP_Customize_Nav_Menu_Name_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-name-control.php' );
 
-/** WP_Customize_Nav_Menu_Auto_Add_Control class */
+/**
+ * WP_Customize_Nav_Menu_Auto_Add_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-auto-add-control.php' );
 
-/** WP_Customize_New_Menu_Control class */
+/**
+ * WP_Customize_New_Menu_Control class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-new-menu-control.php' );
diff --git src/wp-includes/class-wp-customize-manager.php src/wp-includes/class-wp-customize-manager.php
index 669ce05c80..62d587bf6a 100644
--- src/wp-includes/class-wp-customize-manager.php
+++ src/wp-includes/class-wp-customize-manager.php
@@ -2810,11 +2810,27 @@ final class WP_Customize_Manager {
 	 *
 	 * @since 3.4.0
 	 * @since 4.5.0 Return added WP_Customize_Setting instance.
-	 * @access public
 	 *
 	 * @param WP_Customize_Setting|string $id   Customize Setting object, or ID.
-	 * @param array                       $args Setting arguments; passed to WP_Customize_Setting
-	 *                                          constructor.
+	 * @param array                       $args {
+	 *  Optional. Array of properties for the new WP_Customize_Setting. Default empty array.
+	 *
+	 *  @type string       $type                  Type of the setting. Default 'theme_mod'.
+	 *                                            Default 160.
+	 *  @type string       $capability            Capability required for the setting. Default 'edit_theme_options'
+	 *  @type string|array $theme_supports        Theme features required to support the panel. Default is none.
+	 *  @type string       $default               Default value for the setting. Default is empty string.
+	 *  @type string       $transport             Options for rendering the live preview of changes in Theme Customizer.
+	 *                                            Using 'refresh' makes the change visible by reloading the whole preview.
+	 *                                            Using 'postMessage' allows a custom JavaScript to handle live changes.
+	 *                                            @link https://developer.wordpress.org/themes/customize-api
+	 *                                            Default is 'refresh'
+	 *  @type callable     $validate_callback     Server-side validation callback for the setting's value.
+	 *  @type callable     $sanitize_callback     Callback to filter a Customize setting value in un-slashed form.
+	 *  @type callable     $sanitize_js_callback  Callback to convert a Customize PHP setting value to a value that is
+	 *                                            JSON serializable.
+	 *  @type bool         $dirty                 Whether or not the setting is initially dirty when created.
+	 * }
 	 * @return WP_Customize_Setting             The instance of the setting that was added.
 	 */
 	public function add_setting( $id, $args = array() ) {
@@ -2928,11 +2944,19 @@ final class WP_Customize_Manager {
 	 *
 	 * @since 4.0.0
 	 * @since 4.5.0 Return added WP_Customize_Panel instance.
-	 * @access public
 	 *
 	 * @param WP_Customize_Panel|string $id   Customize Panel object, or Panel ID.
-	 * @param array                     $args Optional. Panel arguments. Default empty array.
-	 *
+	 * @param array                     $args {
+	 *  Optional. Array of properties for the new Panel object. Default empty array.
+	 *  @type int          $priority              Priority of the panel, defining the display order of panels and sections.
+	 *                                            Default 160.
+	 *  @type string       $capability            Capability required for the panel. Default `edit_theme_options`
+	 *  @type string|array $theme_supports        Theme features required to support the panel.
+	 *  @type string       $title                 Title of the panel to show in UI.
+	 *  @type string       $description           Description to show in the UI.
+	 *  @type string       $type                  Type of the panel.
+	 *  @type callable     $active_callback       Active callback.
+	 * }
 	 * @return WP_Customize_Panel             The instance of the panel that was added.
 	 */
 	public function add_panel( $id, $args = array() ) {
@@ -3020,8 +3044,19 @@ final class WP_Customize_Manager {
 	 * @access public
 	 *
 	 * @param WP_Customize_Section|string $id   Customize Section object, or Section ID.
-	 * @param array                       $args Section arguments.
-	 *
+	 * @param array                     $args {
+	 *  Optional. Array of properties for the new Panel object. Default empty array.
+	 *  @type int          $priority              Priority of the panel, defining the display order of panels and sections.
+	 *                                            Default 160.
+	 *  @type string       $panel                 Priority of the panel, defining the display order of panels and sections.
+	 *  @type string       $capability            Capability required for the panel. Default 'edit_theme_options'
+	 *  @type string|array $theme_supports        Theme features required to support the panel.
+	 *  @type string       $title                 Title of the panel to show in UI.
+	 *  @type string       $description           Description to show in the UI.
+	 *  @type string       $type                  Type of the panel.
+	 *  @type callable     $active_callback       Active callback.
+	 *  @type bool         $description_hidden    Hide the description behind a help icon, instead of . Default false.
+	 * }
 	 * @return WP_Customize_Section             The instance of the section that was added.
 	 */
 	public function add_section( $id, $args = array() ) {
@@ -3096,8 +3131,26 @@ final class WP_Customize_Manager {
 	 * @access public
 	 *
 	 * @param WP_Customize_Control|string $id   Customize Control object, or ID.
-	 * @param array                       $args Control arguments; passed to WP_Customize_Control
-	 *                                          constructor.
+	 * @param array                       $args {
+	 *  Optional. Array of properties for the new Control object. Default empty array.
+	 *
+	 *  @type array        $settings              All settings tied to the control. If undefined, defaults to `$setting`.
+	 *                                            IDs in the array correspond to the ID of a registered `WP_Customize_Setting`.
+	 *  @type string       $setting               The primary setting for the control (if there is one). Default is 'default'.
+	 *  @type string       $capability            Capability required to use this control. Normally derived from `$settings`.
+	 *  @type int          $priority              Order priority to load the control. Default 10.
+	 *  @type string       $section               The section this control belongs to. Default empty.
+	 *  @type string       $label                 Label for the control. Default empty.
+	 *  @type string       $description           Description for the control. Default empty.
+	 *  @type array        $choices               List of choices for 'radio' or 'select' type controls, where values
+	 *                                            are the keys, and labels are the values. Default empty array.
+	 *  @type array        $input_attrs           List of custom input attributes for control output, where attribute
+	 *                                            names are the keys and values are the values. Default empty array.
+	 *  @type bool         $allow_addition        Show UI for adding new content, currently only used for the
+	 *                                            dropdown-pages control. Default false.
+	 *  @type string       $type                  The type of the control. Default 'text'.
+	 *  @type callback     $active_callback       Active callback.
+	 * }
 	 * @return WP_Customize_Control             The instance of the control that was added.
 	 */
 	public function add_control( $id, $args = array() ) {
@@ -3496,6 +3549,7 @@ final class WP_Customize_Manager {
 	 * Get nonces for the Customizer.
 	 *
 	 * @since 4.5.0
+	 *
 	 * @return array Nonces.
 	 */
 	public function get_nonces() {
@@ -3636,7 +3690,6 @@ final class WP_Customize_Manager {
 	/**
 	 * Returns a list of devices to allow previewing.
 	 *
-	 * @access public
 	 * @since 4.5.0
 	 *
 	 * @return array List of devices with labels and default setting.
@@ -4188,7 +4241,6 @@ final class WP_Customize_Manager {
 	 *
 	 * Used as active callback for static front page section and controls.
 	 *
-	 * @access private
 	 * @since 4.7.0
 	 *
 	 * @returns bool Whether there are published (or to be published) pages.
@@ -4245,7 +4297,6 @@ final class WP_Customize_Manager {
 	 * Callback for validating a background setting value.
 	 *
 	 * @since 4.7.0
-	 * @access private
 	 *
 	 * @param string $value Repeat value.
 	 * @param WP_Customize_Setting $setting Setting.
@@ -4379,7 +4430,6 @@ final class WP_Customize_Manager {
 	 * @see WP_Customize_Manager::register_controls()
 	 *
 	 * @since 4.5.0
-	 * @access private
 	 *
 	 * @return string Custom logo.
 	 */
diff --git src/wp-includes/class-wp-customize-setting.php src/wp-includes/class-wp-customize-setting.php
index 83a5b76d61..8fab457ce3 100644
--- src/wp-includes/class-wp-customize-setting.php
+++ src/wp-includes/class-wp-customize-setting.php
@@ -18,6 +18,9 @@
  */
 class WP_Customize_Setting {
 	/**
+	 * Customizer bootstrap instance.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var WP_Customize_Manager
 	 */
@@ -26,12 +29,16 @@ class WP_Customize_Setting {
 	/**
 	 * Unique string identifier for the setting.
 	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
 	public $id;
 
 	/**
+	 * Type of customize settings.
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
@@ -40,27 +47,69 @@ class WP_Customize_Setting {
 	/**
 	 * Capability required to edit this setting.
 	 *
-	 * @var string
+	 * @since 3.4.0
+	 * @access public
+	 * @var string|array
 	 */
 	public $capability = 'edit_theme_options';
 
 	/**
 	 * Feature a theme is required to support to enable this setting.
 	 *
+	 * @since 3.4.0
+	 * @access public
+	 * @var string
+	 */
+	public $theme_supports = '';
+
+	/**
+	 * The default value for the setting.
+	 *
+	 * @since 3.4.0
+	 * @access public
+	 * @var string
+	 */
+	public $default = '';
+
+	/**
+	 * Options for rendering the live preview of changes in Theme Customizer.
+	 *
+	 * Set this value to 'postMessage' to enable a custom Javascript handler to render changes to this setting
+	 * as opposed to reloading the whole page.
+	 *
+	 * @link https://developer.wordpress.org/themes/customize-api
+	 *
+	 * @since 3.4.0
 	 * @access public
 	 * @var string
 	 */
-	public $theme_supports  = '';
-	public $default         = '';
-	public $transport       = 'refresh';
+	public $transport = 'refresh';
+
+	/**
+	 * Server-side validation callback for the setting's value.
+	 *
+	 * @since 4.6.0
+	 * @access public
+	 * @var callable
+	 */
+	public $validate_callback = '';
+
+	/**
+	 * Callback to filter a Customize setting value in un-slashed form.
+	 *
+	 * @since 3.4.0
+	 * @access public
+	 * @var callable
+	 */
+	public $sanitize_callback = '';
 
 	/**
-	 * Server-side sanitization callback for the setting's value.
+	 * Callback to convert a Customize PHP setting value to a value that is JSON serializable.
 	 *
-	 * @var callback
+	 * @since 3.4.0
+	 * @access public
+	 * @var string
 	 */
-	public $validate_callback    = '';
-	public $sanitize_callback    = '';
 	public $sanitize_js_callback = '';
 
 	/**
@@ -78,6 +127,10 @@ class WP_Customize_Setting {
 	public $dirty = false;
 
 	/**
+	 * ID Data.
+	 *
+	 * @since 3.4.0
+	 * @access protected
 	 * @var array
 	 */
 	protected $id_data = array();
@@ -95,9 +148,9 @@ class WP_Customize_Setting {
 	 * Cache of multidimensional values to improve performance.
 	 *
 	 * @since 4.4.0
+	 * @static
 	 * @access protected
 	 * @var array
-	 * @static
 	 */
 	protected static $aggregated_multidimensionals = array();
 
@@ -168,7 +221,6 @@ class WP_Customize_Setting {
 	 * Get parsed ID data for multidimensional setting.
 	 *
 	 * @since 4.4.0
-	 * @access public
 	 *
 	 * @return array {
 	 *     ID data for multidimensional setting.
@@ -188,7 +240,6 @@ class WP_Customize_Setting {
 	 * calls get combined into one call, greatly improving performance.
 	 *
 	 * @since 4.4.0
-	 * @access protected
 	 */
 	protected function aggregate_multidimensional() {
 		$id_base = $this->id_data['base'];
@@ -216,7 +267,6 @@ class WP_Customize_Setting {
 	 * This is intended only for use by unit tests.
 	 *
 	 * @since 4.5.0
-	 * @access public
 	 * @ignore
 	 */
 	static public function reset_aggregated_multidimensionals() {
@@ -236,7 +286,6 @@ class WP_Customize_Setting {
 	 * Return true if the current site is not the same as the previewed site.
 	 *
 	 * @since 4.2.0
-	 * @access public
 	 *
 	 * @return bool If preview() has been called.
 	 */
@@ -252,6 +301,7 @@ class WP_Customize_Setting {
 	 *
 	 * @see WP_Customize_Setting::preview()
 	 * @since 4.1.1
+	 * @access protected
 	 * @var mixed
 	 */
 	protected $_original_value;
@@ -265,7 +315,6 @@ class WP_Customize_Setting {
 	 *
 	 * @since 3.4.0
 	 * @since 4.4.0 Added boolean return value.
-	 * @access public
 	 *
 	 * @return bool False when preview short-circuits due no change needing to be previewed.
 	 */
@@ -379,7 +428,7 @@ class WP_Customize_Setting {
 	 * is called for this setting.
 	 *
 	 * @since 4.4.0
-	 * @access private
+	 *
 	 * @see WP_Customize_Manager::set_post_value()
 	 * @see WP_Customize_Setting::_multidimensional_preview_filter()
 	 */
@@ -426,7 +475,6 @@ class WP_Customize_Setting {
 	 * the first setting previewed will be used to apply the values for the others.
 	 *
 	 * @since 4.4.0
-	 * @access private
 	 *
 	 * @see WP_Customize_Setting::$aggregated_multidimensionals
 	 * @param mixed $original Original root value.
@@ -469,8 +517,6 @@ class WP_Customize_Setting {
 	 *
 	 * @since 3.4.0
 	 *
-	 * @access public
-	 *
 	 * @return false|void False if cap check fails or value isn't set or is invalid.
 	 */
 	final public function save() {
@@ -536,7 +582,6 @@ class WP_Customize_Setting {
 	 * Validates an input.
 	 *
 	 * @since 4.6.0
-	 * @access public
 	 *
 	 * @see WP_REST_Request::has_valid_params()
 	 *
@@ -578,7 +623,6 @@ class WP_Customize_Setting {
 	 * Get the root value for a setting, especially for multidimensional ones.
 	 *
 	 * @since 4.4.0
-	 * @access protected
 	 *
 	 * @param mixed $default Value to return if root does not exist.
 	 * @return mixed
@@ -603,7 +647,6 @@ class WP_Customize_Setting {
 	 * Set the root value for a setting, especially for multidimensional ones.
 	 *
 	 * @since 4.4.0
-	 * @access protected
 	 *
 	 * @param mixed $value Value to set as root of multidimensional setting.
 	 * @return bool Whether the multidimensional root was updated successfully.
@@ -770,7 +813,6 @@ class WP_Customize_Setting {
 	 * Retrieves the data to export to the client via JSON.
 	 *
 	 * @since 4.6.0
-	 * @access public
 	 *
 	 * @return array Array of parameters passed to JavaScript.
 	 */
@@ -907,17 +949,27 @@ class WP_Customize_Setting {
 	}
 }
 
-/** WP_Customize_Filter_Setting class */
+/**
+ * WP_Customize_Filter_Setting class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-filter-setting.php' );
 
-/** WP_Customize_Header_Image_Setting class */
+/**
+ * WP_Customize_Header_Image_Setting class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-header-image-setting.php' );
 
-/** WP_Customize_Background_Image_Setting class */
+/**
+ * WP_Customize_Background_Image_Setting class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-background-image-setting.php' );
 
-/** WP_Customize_Nav_Menu_Item_Setting class */
+/**
+ * WP_Customize_Nav_Menu_Item_Setting class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-item-setting.php' );
 
-/** WP_Customize_Nav_Menu_Setting class */
+/**
+ * WP_Customize_Nav_Menu_Setting class.
+ */
 require_once( ABSPATH . WPINC . '/customize/class-wp-customize-nav-menu-setting.php' );
diff --git src/wp-includes/customize/class-wp-customize-selective-refresh.php src/wp-includes/customize/class-wp-customize-selective-refresh.php
index 6c04a73698..a1811299d8 100644
--- src/wp-includes/customize/class-wp-customize-selective-refresh.php
+++ src/wp-includes/customize/class-wp-customize-selective-refresh.php
@@ -88,10 +88,29 @@ final class WP_Customize_Selective_Refresh {
 	 * Adds a partial.
 	 *
 	 * @since 4.5.0
-	 * @access public
 	 *
 	 * @param WP_Customize_Partial|string $id   Customize Partial object, or Panel ID.
-	 * @param array                       $args Optional. Partial arguments. Default empty array.
+	 * @param array                       $args {
+	 *  Optional. Array of properties for the new Partials object. Default empty array.
+	 *
+	 *  @type string   $type                  Type of the partial to be created.
+	 *  @type string   $selector              The jQuery selector to find the container element for the partial, that is, a partial's placement.
+	 *  @type array    $settings              IDs for settings tied to the partial.
+	 *  @type string   $primary_setting       The ID for the setting that this partial is primarily responsible for
+	 *                                        rendering. If not supplied, it will default to the ID of the first setting.
+	 *  @type string   $capability            Capability required to edit this partial.
+	 *                                        Normally this is empty and the capability is derived from the capabilities
+	 *                                        of the associated `$settings`.
+	 *  @type callable $render_callback       Render callback.
+	 *                                        Callback is called with one argument, the instance of WP_Customize_Partial.
+	 *                                        The callback can either echo the partial or return the partial as a string,
+	 *                                        or return false if error.
+	 *  @type bool     $container_inclusive   Whether the container element is included in the partial, or if only
+	 *                                        the contents are rendered.
+	 *  @type bool     $fallback_refresh      Whether to refresh the entire preview in case a partial cannot be refreshed.
+	 *                                        A partial render is considered a failure if the render_callback returns
+	 *                                        false.
+	 * }
 	 * @return WP_Customize_Partial             The instance of the panel that was added.
 	 */
 	public function add_partial( $id, $args = array() ) {
