diff --git a/src/Webhooks/Delivery/EventBridge.php b/src/Webhooks/Delivery/EventBridge.php
index 37c105a1..1dedac22 100644
--- a/src/Webhooks/Delivery/EventBridge.php
+++ b/src/Webhooks/Delivery/EventBridge.php
@@ -83,6 +83,6 @@ protected function getMutationName(?string $webhookId): string
      */
     protected function queryEndpoint(string $address): string
     {
-        return "{arn: \"$address\"}";
+        return "arn: \"$address\"";
     }
 }
diff --git a/src/Webhooks/Delivery/HttpDelivery.php b/src/Webhooks/Delivery/HttpDelivery.php
index 13319f39..99406428 100644
--- a/src/Webhooks/Delivery/HttpDelivery.php
+++ b/src/Webhooks/Delivery/HttpDelivery.php
@@ -94,6 +94,6 @@ protected function getMutationName(?string $webhookId): string
      */
     protected function queryEndpoint(string $address): string
     {
-        return "{callbackUrl: \"$address\"}";
+        return "callbackUrl: \"$address\"";
     }
 }
diff --git a/src/Webhooks/Delivery/PubSub.php b/src/Webhooks/Delivery/PubSub.php
index 5cacec28..ffc350fd 100644
--- a/src/Webhooks/Delivery/PubSub.php
+++ b/src/Webhooks/Delivery/PubSub.php
@@ -87,6 +87,6 @@ protected function queryEndpoint(string $address): string
     {
         $addressWithoutProtocol = explode("//", $address);
         list($project, $topic) = explode(":", $addressWithoutProtocol[1]);
-        return "{pubSubProject: \"$project\", pubSubTopic: \"$topic\"}";
+        return "pubSubProject: \"$project\", pubSubTopic: \"$topic\"";
     }
 }
diff --git a/src/Webhooks/DeliveryMethod.php b/src/Webhooks/DeliveryMethod.php
index 89b3becb..65fdf6a7 100644
--- a/src/Webhooks/DeliveryMethod.php
+++ b/src/Webhooks/DeliveryMethod.php
@@ -15,6 +15,8 @@ abstract public function getCallbackAddress(string $path): string;
 
     /**
      * Builds the mutation name to be used depending on the delivery method and webhook id.
+     * If the $webhookId is null, it is assumed that the mutation name is for creating a new subscription.
+     * Otherwise, it is for updating an existing subscription.
      *
      * @param string|null $webhookId
      *
@@ -23,51 +25,75 @@ abstract public function getCallbackAddress(string $path): string;
     abstract protected function getMutationName(?string $webhookId): string;
 
     /**
-     * Assembles a GraphQL query for registering a webhook.
+     * Assembles the webhook subscription arguments based on the callback address.
+     * This allows you to customize the structure of the webhook's subscription data.
      *
-     * @param string $address
+     * @param string $address The callback address for the webhook.
      *
-     * @return string
+     * @return string GraphQL formatted string for the webhook subscription arguments.
      */
     abstract protected function queryEndpoint(string $address): string;
 
     /**
      * Builds a GraphQL query to check whether this topic is already registered for the shop.
+     * This query checks for existing webhook subscriptions for a specific topic.
      *
-     * @param string $topic
+     * @param string $topic The topic to check.
      *
-     * @return string
+     * @return string GraphQL query string to check if a topic is already registered.
      */
     abstract public function buildCheckQuery(string $topic): string;
 
     /**
-     * @param array $body
+     * Parses the result of the check query and returns the webhookId and current delivery address.
+     * This method interprets the response to extract meaningful data, like the webhook ID and its delivery address.
      *
-     * @return array Array of the webhookId and current delivery address
+     * @param array $body The response body from the GraphQL query.
+     *
+     * @return array Array containing the webhookId and current delivery address.
      */
     abstract public function parseCheckQueryResult(array $body): array;
 
     /**
-     * Assembles a GraphQL query for registering a webhook.
+     * Assembles a GraphQL query for registering or updating a webhook subscription.
+     * This method now supports adding additional optional fields and metafield namespaces,
+     * which allows further customization of the webhook subscription.
+     * The operation (create/update) is determined by the webhookId.
      *
-     * @param string      $topic
-     * @param string      $callbackAddress
-     * @param string|null $webhookId
+     * @param string      $topic               The topic for the webhook subscription.
+     * @param string      $callbackAddress     The callback URL for the webhook.
+     * @param string|null $webhookId           Optional webhook ID for updating an existing subscription.
+     * @param array       $fields              Optional fields to include in the webhook subscription.
+     * @param array       $metafieldNamespaces Optional metafield namespaces to include.
      *
-     * @return string
+     * @return string The GraphQL query to register or update the webhook.
      */
     public function buildRegisterQuery(
         string $topic,
         string $callbackAddress,
-        ?string $webhookId = null
+        ?string $webhookId = null,
+        array $fields = [],
+        array $metafieldNamespaces = []
     ): string {
         $mutationName = $this->getMutationName($webhookId);
         $identifier = $webhookId ? "id: \"$webhookId\"" : "topic: $topic";
         $webhookSubscriptionArgs = $this->queryEndpoint($callbackAddress);
 
+        $query = "$identifier, webhookSubscription: {{$webhookSubscriptionArgs}";
+
+        if (!empty($fields)) {
+            $query .= ' fields: [' . implode(',', $fields) . ']';
+        }
+
+        if (!empty($metafieldNamespaces)) {
+            $query .= ' metafieldNamespaces: [' . implode(',', $metafieldNamespaces) . ']';
+        }
+
+        $query .= "}";
+
         return <<<QUERY
         mutation webhookSubscription {
-            $mutationName($identifier, webhookSubscription: $webhookSubscriptionArgs) {
+            $mutationName($query) {
                 userErrors {
                     field
                     message
@@ -79,14 +105,15 @@ public function buildRegisterQuery(
         }
         QUERY;
     }
-
     /**
-     * Checks if the given result was successful.
+     * Checks if the given result indicates a successful registration or update of the webhook subscription.
+     * 
+     * This method inspects the GraphQL response to determine whether the operation succeeded.
      *
-     * @param array       $result
-     * @param string|null $webhookId
+     * @param array       $result    The response array from the GraphQL query.
+     * @param string|null $webhookId Optional webhook ID to distinguish between create and update mutations.
      *
-     * @return bool
+     * @return bool True if the operation was successful, otherwise false.
      */
     public function isSuccess(array $result, ?string $webhookId = null): bool
     {
diff --git a/src/Webhooks/Registry.php b/src/Webhooks/Registry.php
index fc9edc21..fe6ff7ba 100644
--- a/src/Webhooks/Registry.php
+++ b/src/Webhooks/Registry.php
@@ -59,12 +59,15 @@ public static function getHandler(string $topic): ?Handler
     /**
      * Registers a new webhook for this app with Shopify.
      *
-     * @param string        $path           The URL path for the callback. If using EventBridge, this is the full
-     *                                      resource address
-     * @param string        $topic          The topic to subscribe to. May be a string or a value from the Topics class
-     * @param string        $shop           The shop to use for requests
-     * @param string        $accessToken    The access token to use for requests
-     * @param string|null   $deliveryMethod The delivery method for this webhook. Defaults to HTTP
+     * @param string        $path                The URL path for the callback. If using EventBridge, this is the full
+     *                                           resource address
+     * @param string        $topic               The topic to subscribe to. Can be a string or a value from
+     *                                           the Topics class
+     * @param string        $shop                The shop to use for requests
+     * @param string        $accessToken         The access token to use for requests
+     * @param string|null   $deliveryMethod      The delivery method for this webhook. Defaults to HTTP
+     * @param array         $fields              The fields to request in the webhook
+     * @param array         $metafieldNamespaces The metafield namespaces to request in the webhook
      *
      * @return RegisterResponse
      * @throws ClientExceptionInterface
@@ -77,7 +80,9 @@ public static function register(
         string $topic,
         string $shop,
         string $accessToken,
-        ?string $deliveryMethod = self::DELIVERY_METHOD_HTTP
+        ?string $deliveryMethod = self::DELIVERY_METHOD_HTTP,
+        array $fields = [],
+        array $metafieldNamespaces = []
     ): RegisterResponse {
         /** @var DeliveryMethod */
         $method = null;
@@ -114,7 +119,9 @@ public static function register(
                 $topic,
                 $callbackAddress,
                 $method,
-                $webhookId
+                $webhookId,
+                $fields,
+                $metafieldNamespaces
             );
             $registered = $method->isSuccess($body, $webhookId);
         }
@@ -228,10 +235,20 @@ private static function sendRegisterRequest(
         string $topic,
         string $callbackAddress,
         DeliveryMethod $deliveryMethod,
-        ?string $webhookId
+        ?string $webhookId,
+        array $fields = [],
+        array $metafieldNamespaces = []
     ): array {
+        $registerQuery = $deliveryMethod->buildRegisterQuery(
+            $topic,
+            $callbackAddress,
+            $webhookId,
+            $fields,
+            $metafieldNamespaces
+        );
+
         $registerResponse = $client->query(
-            data: $deliveryMethod->buildRegisterQuery($topic, $callbackAddress, $webhookId),
+            data: $registerQuery,
         );
 
         $statusCode = $registerResponse->getStatusCode();
diff --git a/tests/Clients/GraphqlTest.php b/tests/Clients/GraphqlTest.php
index f31b2b5f..62e6d7c4 100644
--- a/tests/Clients/GraphqlTest.php
+++ b/tests/Clients/GraphqlTest.php
@@ -201,11 +201,12 @@ public function testCanQueryWithExtraHeaders()
     public function testProxyForwardsBodyAsJsonType()
     {
         $queryToProxy = <<<QUERY
+        <<<QUERY
         {
-          "variables": {},
-          "query": "{\nshop {\n    name\n    __typename\n  }\n}"
+            "variables": {},
+            "query": "{\nshop {\n    name\n    __typename\n  }\n}"
         }
-        QUERY;
+        QUERY; // phpcs:ignore
 
         $extraHeaders = ['Extra-Extra' => 'hear_all_about_it'];
         $client = new Graphql($this->domain, 'token');