diff --git a/includes/interfaces/class-wc-abstract-order-data-store-interface.php b/includes/interfaces/class-wc-abstract-order-data-store-interface.php
index b1ed0b703c7..a511b705661 100644
--- a/includes/interfaces/class-wc-abstract-order-data-store-interface.php
+++ b/includes/interfaces/class-wc-abstract-order-data-store-interface.php
@@ -26,7 +26,7 @@ interface WC_Abstract_Order_Data_Store_Interface {
 	/**
 	 * Remove all line items (products, coupons, shipping, taxes) from the order.
 	 *
-	 * @param WC_Order
+	 * @param WC_Order $order
 	 * @param string $type Order item type. Default null.
 	 */
 	public function delete_items( $order, $type = null );
@@ -34,7 +34,7 @@ interface WC_Abstract_Order_Data_Store_Interface {
 	/**
 	 * Get token ids for an order.
 	 *
-	 * @param WC_Order
+	 * @param WC_Order $order
 	 * @return array
 	 */
 	public function get_payment_token_ids( $order );
@@ -42,7 +42,7 @@ interface WC_Abstract_Order_Data_Store_Interface {
 	/**
 	 * Update token ids for an order.
 	 *
-	 * @param WC_Order
+	 * @param WC_Order $order
 	 * @param array $token_ids
 	 */
 	public function update_payment_token_ids( $order, $token_ids );
diff --git a/includes/interfaces/class-wc-coupon-data-store-interface.php b/includes/interfaces/class-wc-coupon-data-store-interface.php
index 0dcb4839373..d4174ba203b 100644
--- a/includes/interfaces/class-wc-coupon-data-store-interface.php
+++ b/includes/interfaces/class-wc-coupon-data-store-interface.php
@@ -15,22 +15,22 @@ if ( ! defined( 'ABSPATH' ) ) {
 interface WC_Coupon_Data_Store_Interface {
 	/**
 	 * Increase usage count for current coupon.
-	 * @param WC_Coupon
+	 * @param WC_Coupon &$coupon
 	 * @param string $used_by Either user ID or billing email
 	 */
 	public function increase_usage_count( &$coupon, $used_by = '' );
 
 	/**
 	 *  Decrease usage count for current coupon.
-	 * @param WC_Coupon
+	 * @param WC_Coupon &$coupon
 	 * @param string $used_by Either user ID or billing email
 	 */
 	public function decrease_usage_count( &$coupon, $used_by = '' );
 
 	/**
 	 * Get the number of uses for a coupon by user ID.
-	 * @param WC_Coupon
-	 * @param id $user_id
+	 * @param WC_Coupon &$coupon
+	 * @param int $user_id
 	 * @return int
 	 */
 	public function get_usage_by_user_id( &$coupon, $user_id );
diff --git a/includes/interfaces/class-wc-customer-data-store-interface.php b/includes/interfaces/class-wc-customer-data-store-interface.php
index 163770e823e..7ed1cca6722 100644
--- a/includes/interfaces/class-wc-customer-data-store-interface.php
+++ b/includes/interfaces/class-wc-customer-data-store-interface.php
@@ -17,7 +17,7 @@ interface WC_Customer_Data_Store_Interface {
 	/**
 	 * Gets the customers last order.
 	 *
-	 * @param WC_Customer
+	 * @param WC_Customer &$customer
 	 * @return WC_Order|false
 	 */
 	public function get_last_order( &$customer );
@@ -25,7 +25,7 @@ interface WC_Customer_Data_Store_Interface {
 	/**
 	 * Return the number of orders this customer has.
 	 *
-	 * @param WC_Customer
+	 * @param WC_Customer &$customer
 	 * @return integer
 	 */
 	public function get_order_count( &$customer );
@@ -33,7 +33,7 @@ interface WC_Customer_Data_Store_Interface {
 	/**
 	 * Return how much money this customer has spent.
 	 *
-	 * @param WC_Customer
+	 * @param WC_Customer &$customer
 	 * @return float
 	 */
 	public function get_total_spent( &$customer );
diff --git a/includes/interfaces/class-wc-object-data-store-interface.php b/includes/interfaces/class-wc-object-data-store-interface.php
index 145eefba4ff..50a0e842fcd 100644
--- a/includes/interfaces/class-wc-object-data-store-interface.php
+++ b/includes/interfaces/class-wc-object-data-store-interface.php
@@ -13,25 +13,25 @@ if ( ! defined( 'ABSPATH' ) ) {
 interface WC_Object_Data_Store_Interface {
 	/**
 	 * Method to create a new record of a WC_Data based object.
-	 * @param WC_Data
+	 * @param WC_Data &$data
 	 */
 	public function create( &$data );
 
 	/**
 	 * Method to read a record. Creates a new WC_Data based object.
-	 * @param WC_Data
+	 * @param WC_Data &$data
 	 */
 	public function read( &$data );
 
 	/**
 	 * Updates a record in the database.
-	 * @param WC_Data
+	 * @param WC_Data &$data
 	 */
 	public function update( &$data );
 
 	/**
 	 * Deletes a record from the database.
-	 * @param  WC_Data
+	 * @param  WC_Data &$data
 	 * @param  array $args Array of args to pass to the delete method.
 	 * @return bool result
 	 */
@@ -39,31 +39,31 @@ interface WC_Object_Data_Store_Interface {
 
 	/**
 	 * Returns an array of meta for an object.
-	 * @param  WC_Data
+	 * @param  WC_Data &$data
 	 * @return array
 	 */
 	public function read_meta( &$data );
 
 	/**
 	 * Deletes meta based on meta ID.
-	 * @param  WC_Data
-	 * @param  stdClass (containing at least ->id)
+	 * @param  WC_Data &$data
+	 * @param  object $meta (containing at least ->id)
 	 * @return array
 	 */
 	public function delete_meta( &$data, $meta );
 
 	/**
 	 * Add new piece of meta.
-	 * @param  WC_Data
-	 * @param  stdClass (containing ->key and ->value)
-	 * @return meta ID
+	 * @param  WC_Data &$data
+	 * @param  object $meta (containing ->key and ->value)
+	 * @return int meta ID
 	 */
 	public function add_meta( &$data, $meta );
 
 	/**
 	 * Update meta.
-	 * @param  WC_Data
-	 * @param  stdClass (containing ->id, ->key and ->value)
+	 * @param  WC_Data &$data
+	 * @param  object $meta (containing ->id, ->key and ->value)
 	 */
 	public function update_meta( &$data, $meta );
 }
diff --git a/includes/interfaces/class-wc-order-data-store-interface.php b/includes/interfaces/class-wc-order-data-store-interface.php
index f45c14e45e2..2928aee9651 100644
--- a/includes/interfaces/class-wc-order-data-store-interface.php
+++ b/includes/interfaces/class-wc-order-data-store-interface.php
@@ -16,7 +16,7 @@ interface WC_Order_Data_Store_Interface {
 	/**
 	 * Get amount already refunded.
 	 *
-	 * @param  WC_Order
+	 * @param  WC_Order $order
 	 * @return string
 	 */
 	public function get_total_refunded( $order );
@@ -24,7 +24,7 @@ interface WC_Order_Data_Store_Interface {
 	/**
 	 * Get the total tax refunded.
 	 *
-	 * @param  WC_Order
+	 * @param  WC_Order $order
 	 * @return float
 	 */
 	public function get_total_tax_refunded( $order );
@@ -32,7 +32,7 @@ interface WC_Order_Data_Store_Interface {
 	/**
 	 * Get the total shipping refunded.
 	 *
-	 * @param  WC_Order
+	 * @param  WC_Order $order
 	 * @return float
 	 */
 	public function get_total_shipping_refunded( $order );
@@ -63,7 +63,7 @@ interface WC_Order_Data_Store_Interface {
 
 	/**
 	 * Get unpaid orders after a certain date,
-	 * @param  int timestamp $date
+	 * @param  int $date timestamp
 	 * @return array
 	 */
 	public function get_unpaid_orders( $date );
diff --git a/includes/interfaces/class-wc-payment-token-data-store-interface.php b/includes/interfaces/class-wc-payment-token-data-store-interface.php
index bb40bafefd5..9a878617e8f 100644
--- a/includes/interfaces/class-wc-payment-token-data-store-interface.php
+++ b/includes/interfaces/class-wc-payment-token-data-store-interface.php
@@ -25,7 +25,7 @@ interface WC_Payment_Token_Data_Store_Interface {
 	/**
 	 * Returns an stdObject of a token for a user's default token.
 	 * Should contain the fields token_id, gateway_id, token, user_id, type, is_default.
-	 * @param id $user_id
+	 * @param int $user_id
 	 * @return object
 	 */
 	public function get_users_default_token( $user_id );
@@ -33,14 +33,14 @@ interface WC_Payment_Token_Data_Store_Interface {
 	/**
 	 * Returns an stdObject of a token.
 	 * Should contain the fields token_id, gateway_id, token, user_id, type, is_default.
-	 * @param id $token_id
+	 * @param int $token_id
 	 * @return object
 	 */
 	public function get_token_by_id( $token_id );
 
 	/**
 	 * Returns metadata for a specific payment token.
-	 * @param id $token_id
+	 * @param int $token_id
 	 * @return array
 	 */
 	public function get_metadata( $token_id );
@@ -49,7 +49,7 @@ interface WC_Payment_Token_Data_Store_Interface {
 	 * Get a token's type by ID.
 	 *
 	 * @since 3.0.0
-	 * @param id $token_id
+	 * @param int $token_id
 	 * @return string
 	 */
 	public function get_token_type_by_id( $token_id );
@@ -58,7 +58,8 @@ interface WC_Payment_Token_Data_Store_Interface {
 	 * Update's a tokens default status in the database. Used for quickly
 	 * looping through tokens and setting their statuses instead of creating a bunch
 	 * of objects.
-	 * @param id $token_id
+	 * @param int $token_id
+	 * @param bool $status
 	 * @return string
 	 */
 	public function set_default_status( $token_id, $status = true );
diff --git a/includes/interfaces/class-wc-product-data-store-interface.php b/includes/interfaces/class-wc-product-data-store-interface.php
index 2852a0bbd01..2bfd73096db 100644
--- a/includes/interfaces/class-wc-product-data-store-interface.php
+++ b/includes/interfaces/class-wc-product-data-store-interface.php
@@ -95,7 +95,7 @@ interface WC_Product_Data_Store_Interface {
 	 *
 	 * Uses queries rather than update_post_meta so we can do this in one query (to avoid stock issues).
 	 *
-	 * @param  int
+	 * @param  int $product_id_with_stock
 	 * @param  int|null $stock_quantity
 	 * @param  string $operation set, increase and decrease.
 	 */
@@ -107,7 +107,7 @@ interface WC_Product_Data_Store_Interface {
 	 * Uses queries rather than update_post_meta so we can do this in one query for performance.
 	 *
 	 * @since  3.0.0 this supports set, increase and decrease.
-	 * @param  int
+	 * @param  int $product_id
 	 * @param  int|null $quantity
 	 * @param  string $operation set, increase and decrease.
 	 */
@@ -115,7 +115,7 @@ interface WC_Product_Data_Store_Interface {
 
 	/**
 	 * Get shipping class ID by slug.
-	 * @param $slug string
+	 * @param string $slug
 	 * @return int|false
 	 */
 	public function get_shipping_class_id_by_slug( $slug );
diff --git a/includes/interfaces/class-wc-product-variable-data-store-interface.php b/includes/interfaces/class-wc-product-variable-data-store-interface.php
index 33171ce7894..b327abfb4de 100644
--- a/includes/interfaces/class-wc-product-variable-data-store-interface.php
+++ b/includes/interfaces/class-wc-product-variable-data-store-interface.php
@@ -66,7 +66,7 @@ interface WC_Product_Variable_Data_Store_Interface {
 	 * Delete variations of a product.
 	 *
 	 * @param int $product_id
-	 * @param $force_delete False to trash.
+	 * @param bool $force_delete False to trash.
 	 */
 	public function delete_variations( $product_id, $force_delete = false );
 
diff --git a/includes/interfaces/class-wc-shipping-zone-data-store-interface.php b/includes/interfaces/class-wc-shipping-zone-data-store-interface.php
index 05cc0759456..b488f778b61 100644
--- a/includes/interfaces/class-wc-shipping-zone-data-store-interface.php
+++ b/includes/interfaces/class-wc-shipping-zone-data-store-interface.php
@@ -23,7 +23,7 @@ interface WC_Shipping_Zone_Data_Store_Interface {
 
 	/**
 	 * Get count of methods for a zone.
-	 * @param  int Zone ID
+	 * @param  int $zone_id Zone ID
 	 * @return int Method Count
 	 */
 	public function get_method_count( $zone_id );