diff --git a/src/mcp-sdk/src/Capability/Tool/ToolCallResult.php b/src/mcp-sdk/src/Capability/Tool/ToolCallResult.php
index 2bdd2d0d..79ee4344 100644
--- a/src/mcp-sdk/src/Capability/Tool/ToolCallResult.php
+++ b/src/mcp-sdk/src/Capability/Tool/ToolCallResult.php
@@ -14,12 +14,12 @@
 final readonly class ToolCallResult
 {
     public function __construct(
-        public string $result,
+        public mixed $result,
         /**
          * @var "text"|"image"|"audio"|"resource"|non-empty-string
          */
         public string $type = 'text',
-        public string $mimeType = 'text/plan',
+        public string $mimeType = 'text/plain',
         public bool $isError = false,
         public ?string $uri = null,
     ) {
diff --git a/src/mcp-sdk/src/Server/RequestHandler/ToolCallHandler.php b/src/mcp-sdk/src/Server/RequestHandler/ToolCallHandler.php
index 49c16562..c56a563c 100644
--- a/src/mcp-sdk/src/Server/RequestHandler/ToolCallHandler.php
+++ b/src/mcp-sdk/src/Server/RequestHandler/ToolCallHandler.php
@@ -26,6 +26,9 @@ public function __construct(
     ) {
     }
 
+    /**
+     * @throws \JsonException
+     */
     public function createResponse(Request $message): Response|Error
     {
         $name = $message->params['name'];
@@ -40,7 +43,7 @@ public function createResponse(Request $message): Response|Error
         $content = match ($result->type) {
             'text' => [
                 'type' => 'text',
-                'text' => $result->result,
+                'text' => json_encode($result->result, \JSON_THROW_ON_ERROR),
             ],
             'image', 'audio' => [
                 'type' => $result->type,
@@ -59,10 +62,16 @@ public function createResponse(Request $message): Response|Error
             default => throw new InvalidArgumentException('Unsupported tool result type: '.$result->type),
         };
 
-        return new Response($message->id, [
+        $response = [
             'content' => [$content], // TODO: allow multiple `ToolCallResult`s in the future
             'isError' => $result->isError,
-        ]);
+        ];
+
+        if ('text' === $result->type && \is_array($result->result) || \is_object($result->result)) {
+            $response['structuredContent'] = $result->result;
+        }
+
+        return new Response($message->id, $response);
     }
 
     protected function supportedMethod(): string