diff --git a/src/Client/CancelRetryClient.php b/src/Client/CancelRetryClient.php
index 9ae7ffe..9c1bea3 100644
--- a/src/Client/CancelRetryClient.php
+++ b/src/Client/CancelRetryClient.php
@@ -39,7 +39,7 @@ public function buildApiUrl(): string
     /**
      * Builds array for CURLOPT_POSTFIELDS curl argument.
      *
-     * @return array<string, string>
+     * @return array{token: string}
      */
     public function buildCurlPostFields(Receipt $receipt): array
     {
diff --git a/src/Client/SubscriptionClient.php b/src/Client/SubscriptionClient.php
index e84d118..b88acbb 100644
--- a/src/Client/SubscriptionClient.php
+++ b/src/Client/SubscriptionClient.php
@@ -36,7 +36,7 @@ public function buildApiUrl(): string
     /**
      * Builds array for CURLOPT_POSTFIELDS curl argument.
      *
-     * @return array<string, string>
+     * @return array{token: string, subscription: string, user: string, device_name?: string, sound?: string}
      */
     public function buildCurlPostFields(Subscription $subscription, Recipient $recipient, ?Sound $sound = null): array
     {
diff --git a/src/Client/UserGroupValidationClient.php b/src/Client/UserGroupValidationClient.php
index 56c6d11..c05c350 100644
--- a/src/Client/UserGroupValidationClient.php
+++ b/src/Client/UserGroupValidationClient.php
@@ -33,7 +33,7 @@ public function buildApiUrl(): string
     /**
      * Builds array for CURLOPT_POSTFIELDS curl argument.
      *
-     * @return array<string, string>
+     * @return array{token: string, user: string, device?: string}
      */
     public function buildCurlPostFields(Application $application, Recipient $recipient): array
     {