diff --git a/examples/server/conformance/Elements.php b/examples/server/conformance/Elements.php
index 81d25b32..b7f74ff2 100644
--- a/examples/server/conformance/Elements.php
+++ b/examples/server/conformance/Elements.php
@@ -11,13 +11,13 @@
 
 namespace Mcp\Example\Server\Conformance;
 
-use Mcp\Schema\Content\Content;
 use Mcp\Schema\Content\EmbeddedResource;
 use Mcp\Schema\Content\ImageContent;
 use Mcp\Schema\Content\PromptMessage;
 use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\Content\TextResourceContents;
 use Mcp\Schema\Enum\Role;
+use Mcp\Schema\Result\CallToolResult;
 use Mcp\Server\Protocol;
 use Mcp\Server\RequestContext;
 
@@ -28,12 +28,9 @@ final class Elements
     // Sample base64 encoded minimal WAV file for testing
     public const TEST_AUDIO_BASE64 = 'UklGRiYAAABXQVZFZm10IBAAAAABAAEAQB8AAAB9AAACABAAZGF0YQIAAAA=';
 
-    /**
-     * @return Content[]
-     */
-    public function toolMultipleTypes(): array
+    public function toolMultipleTypes(): CallToolResult
     {
-        return [
+        return new CallToolResult([
             new TextContent('Multiple content types test:'),
             new ImageContent(self::TEST_IMAGE_BASE64, 'image/png'),
             EmbeddedResource::fromText(
@@ -41,7 +38,7 @@ public function toolMultipleTypes(): array
                 '{ "test" = "data", "value" = 123 }',
                 'application/json',
             ),
-        ];
+        ]);
     }
 
     public function toolWithLogging(RequestContext $context): string
diff --git a/examples/server/env-variables/EnvToolHandler.php b/examples/server/env-variables/EnvToolHandler.php
index 7c6cc8df..c11c6633 100644
--- a/examples/server/env-variables/EnvToolHandler.php
+++ b/examples/server/env-variables/EnvToolHandler.php
@@ -23,7 +23,31 @@ final class EnvToolHandler
      *
      * @return array<string, string|int> the result, varying by APP_MODE
      */
-    #[McpTool(name: 'process_data_by_mode')]
+    #[McpTool(
+        name: 'process_data_by_mode',
+        outputSchema: [
+            'type' => 'object',
+            'properties' => [
+                'mode' => [
+                    'type' => 'string',
+                    'description' => 'The processing mode used',
+                ],
+                'processed_input' => [
+                    'type' => 'string',
+                    'description' => 'The processed input data',
+                ],
+                'original_input' => [
+                    'type' => 'string',
+                    'description' => 'The original input data (only in default mode)',
+                ],
+                'message' => [
+                    'type' => 'string',
+                    'description' => 'A descriptive message about the processing',
+                ],
+            ],
+            'required' => ['mode', 'message'],
+        ]
+    )]
     public function processData(string $input): array
     {
         $appMode = getenv('APP_MODE'); // Read from environment
diff --git a/src/Capability/Attribute/McpTool.php b/src/Capability/Attribute/McpTool.php
index 85dbc225..fe754e90 100644
--- a/src/Capability/Attribute/McpTool.php
+++ b/src/Capability/Attribute/McpTool.php
@@ -21,11 +21,12 @@
 class McpTool
 {
     /**
-     * @param string|null           $name        The name of the tool (defaults to the method name)
-     * @param string|null           $description The description of the tool (defaults to the DocBlock/inferred)
-     * @param ToolAnnotations|null  $annotations Optional annotations describing tool behavior
-     * @param ?Icon[]               $icons       Optional list of icon URLs representing the tool
-     * @param ?array<string, mixed> $meta        Optional metadata
+     * @param string|null           $name         The name of the tool (defaults to the method name)
+     * @param string|null           $description  The description of the tool (defaults to the DocBlock/inferred)
+     * @param ToolAnnotations|null  $annotations  Optional annotations describing tool behavior
+     * @param ?Icon[]               $icons        Optional list of icon URLs representing the tool
+     * @param ?array<string, mixed> $meta         Optional metadata
+     * @param array<string, mixed>  $outputSchema Optional JSON Schema object for defining the expected output structure
      */
     public function __construct(
         public ?string $name = null,
@@ -33,6 +34,7 @@ public function __construct(
         public ?ToolAnnotations $annotations = null,
         public ?array $icons = null,
         public ?array $meta = null,
+        public ?array $outputSchema = null,
     ) {
     }
 }
diff --git a/src/Capability/Discovery/Discoverer.php b/src/Capability/Discovery/Discoverer.php
index 95a3fe5a..74031e56 100644
--- a/src/Capability/Discovery/Discoverer.php
+++ b/src/Capability/Discovery/Discoverer.php
@@ -222,6 +222,7 @@ private function processMethod(\ReflectionMethod $method, array &$discoveredCoun
                     $name = $instance->name ?? ('__invoke' === $methodName ? $classShortName : $methodName);
                     $description = $instance->description ?? $this->docBlockParser->getSummary($docBlock) ?? null;
                     $inputSchema = $this->schemaGenerator->generate($method);
+                    $outputSchema = $this->schemaGenerator->generateOutputSchema($method);
                     $tool = new Tool(
                         $name,
                         $inputSchema,
@@ -229,6 +230,7 @@ private function processMethod(\ReflectionMethod $method, array &$discoveredCoun
                         $instance->annotations,
                         $instance->icons,
                         $instance->meta,
+                        $outputSchema,
                     );
                     $tools[$name] = new ToolReference($tool, [$className, $methodName], false);
                     ++$discoveredCount['tools'];
diff --git a/src/Capability/Discovery/SchemaGenerator.php b/src/Capability/Discovery/SchemaGenerator.php
index 0676e8d9..f711a0d0 100644
--- a/src/Capability/Discovery/SchemaGenerator.php
+++ b/src/Capability/Discovery/SchemaGenerator.php
@@ -11,6 +11,7 @@
 
 namespace Mcp\Capability\Discovery;
 
+use Mcp\Capability\Attribute\McpTool;
 use Mcp\Capability\Attribute\Schema;
 use Mcp\Exception\InvalidArgumentException;
 use Mcp\Server\RequestContext;
@@ -81,6 +82,28 @@ public function generate(\ReflectionMethod|\ReflectionFunction $reflection): arr
         return $this->buildSchemaFromParameters($parametersInfo, $methodSchema);
     }
 
+    /**
+     * Generates a JSON Schema object (as a PHP array) for a method's or function's return type.
+     *
+     * Only returns an outputSchema if explicitly provided in the McpTool attribute.
+     * Per MCP spec, outputSchema should only be present when explicitly provided.
+     *
+     * @return array<string, mixed>|null
+     */
+    public function generateOutputSchema(\ReflectionMethod|\ReflectionFunction $reflection): ?array
+    {
+        // Only return outputSchema if explicitly provided in McpTool attribute
+        $mcpToolAttrs = $reflection->getAttributes(McpTool::class, \ReflectionAttribute::IS_INSTANCEOF);
+        if (!empty($mcpToolAttrs)) {
+            $mcpToolInstance = $mcpToolAttrs[0]->newInstance();
+            if (null !== $mcpToolInstance->outputSchema) {
+                return $mcpToolInstance->outputSchema;
+            }
+        }
+
+        return null;
+    }
+
     /**
      * Extracts method-level or function-level Schema attribute.
      *
diff --git a/src/Capability/Registry/Loader/ArrayLoader.php b/src/Capability/Registry/Loader/ArrayLoader.php
index fef17263..f23e5270 100644
--- a/src/Capability/Registry/Loader/ArrayLoader.php
+++ b/src/Capability/Registry/Loader/ArrayLoader.php
@@ -47,7 +47,8 @@ final class ArrayLoader implements LoaderInterface
      *     description: ?string,
      *     annotations: ?ToolAnnotations,
      *     icons: ?Icon[],
-     *     meta: ?array<string, mixed>
+     *     meta: ?array<string, mixed>,
+     *     outputSchema: ?array<string, mixed>
      * }[] $tools
      * @param array{
      *     handler: Handler,
@@ -117,6 +118,7 @@ public function load(RegistryInterface $registry): void
                     annotations: $data['annotations'] ?? null,
                     icons: $data['icons'] ?? null,
                     meta: $data['meta'] ?? null,
+                    outputSchema: $data['outputSchema'] ?? null,
                 );
                 $registry->registerTool($tool, $data['handler'], true);
 
diff --git a/src/Capability/Registry/ToolReference.php b/src/Capability/Registry/ToolReference.php
index e5b5a7df..bc750b1d 100644
--- a/src/Capability/Registry/ToolReference.php
+++ b/src/Capability/Registry/ToolReference.php
@@ -111,4 +111,33 @@ public function formatResult(mixed $toolExecutionResult): array
 
         return [new TextContent($jsonResult)];
     }
+
+    /**
+     * Extracts structured content from a tool result using the output schema.
+     *
+     * @param mixed $toolExecutionResult the raw value returned by the tool's PHP method
+     *
+     * @return array<string, mixed>|null the structured content, or null if not extractable
+     *
+     * @throws \JsonException if JSON encoding fails for non-Content array/object results
+     */
+    public function extractStructuredContent(mixed $toolExecutionResult): ?array
+    {
+        if (\is_array($toolExecutionResult)) {
+            return $toolExecutionResult;
+        }
+
+        if (\is_object($toolExecutionResult) && !($toolExecutionResult instanceof Content)) {
+            $jsonResult = json_encode(
+                $toolExecutionResult,
+                \JSON_PRETTY_PRINT | \JSON_UNESCAPED_SLASHES | \JSON_UNESCAPED_UNICODE | \JSON_THROW_ON_ERROR | \JSON_INVALID_UTF8_SUBSTITUTE
+            );
+
+            return json_decode(
+                $jsonResult, true, 512, \JSON_THROW_ON_ERROR
+            );
+        }
+
+        return null;
+    }
 }
diff --git a/src/Schema/Result/CallToolResult.php b/src/Schema/Result/CallToolResult.php
index 4f31e034..bfbc9fab 100644
--- a/src/Schema/Result/CallToolResult.php
+++ b/src/Schema/Result/CallToolResult.php
@@ -83,6 +83,7 @@ public static function error(array $content, ?array $meta = null): self
      *     content: array<mixed>,
      *     isError?: bool,
      *     _meta?: array<string, mixed>,
+     *     structuredContent?: array<string, mixed>
      * } $data
      */
     public static function fromArray(array $data): self
diff --git a/src/Schema/Tool.php b/src/Schema/Tool.php
index 3a4e8193..4a1768ee 100644
--- a/src/Schema/Tool.php
+++ b/src/Schema/Tool.php
@@ -24,13 +24,21 @@
  *     properties: array<string, mixed>,
  *     required: string[]|null
  * }
+ * @phpstan-type ToolOutputSchema array{
+ *     type: 'object',
+ *     properties?: array<string, mixed>,
+ *     required?: string[]|null,
+ *     additionalProperties?: bool|array<string, mixed>,
+ *     description?: string
+ * }
  * @phpstan-type ToolData array{
  *     name: string,
  *     inputSchema: ToolInputSchema,
  *     description?: string|null,
  *     annotations?: ToolAnnotationsData,
  *     icons?: IconData[],
- *     _meta?: array<string, mixed>
+ *     _meta?: array<string, mixed>,
+ *     outputSchema?: ToolOutputSchema
  * }
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
@@ -38,14 +46,15 @@
 class Tool implements \JsonSerializable
 {
     /**
-     * @param string                $name        the name of the tool
-     * @param ?string               $description A human-readable description of the tool.
-     *                                           This can be used by clients to improve the LLM's understanding of
-     *                                           available tools. It can be thought of like a "hint" to the model.
-     * @param ToolInputSchema       $inputSchema a JSON Schema object (as a PHP array) defining the expected 'arguments' for the tool
-     * @param ?ToolAnnotations      $annotations optional additional tool information
-     * @param ?Icon[]               $icons       optional icons representing the tool
-     * @param ?array<string, mixed> $meta        Optional metadata
+     * @param string                $name         the name of the tool
+     * @param ?string               $description  A human-readable description of the tool.
+     *                                            This can be used by clients to improve the LLM's understanding of
+     *                                            available tools. It can be thought of like a "hint" to the model.
+     * @param ToolInputSchema       $inputSchema  a JSON Schema object (as a PHP array) defining the expected 'arguments' for the tool
+     * @param ?ToolAnnotations      $annotations  optional additional tool information
+     * @param ?Icon[]               $icons        optional icons representing the tool
+     * @param ?array<string, mixed> $meta         Optional metadata
+     * @param ToolOutputSchema|null $outputSchema optional JSON Schema object (as a PHP array) defining the expected output structure
      */
     public function __construct(
         public readonly string $name,
@@ -54,6 +63,7 @@ public function __construct(
         public readonly ?ToolAnnotations $annotations,
         public readonly ?array $icons = null,
         public readonly ?array $meta = null,
+        public readonly ?array $outputSchema = null,
     ) {
         if (!isset($inputSchema['type']) || 'object' !== $inputSchema['type']) {
             throw new InvalidArgumentException('Tool inputSchema must be a JSON Schema of type "object".');
@@ -78,13 +88,23 @@ public static function fromArray(array $data): self
             $data['inputSchema']['properties'] = new \stdClass();
         }
 
+        if (isset($data['outputSchema']) && \is_array($data['outputSchema'])) {
+            if (!isset($data['outputSchema']['type']) || 'object' !== $data['outputSchema']['type']) {
+                throw new InvalidArgumentException('Tool outputSchema must be of type "object".');
+            }
+            if (isset($data['outputSchema']['properties']) && \is_array($data['outputSchema']['properties']) && empty($data['outputSchema']['properties'])) {
+                $data['outputSchema']['properties'] = new \stdClass();
+            }
+        }
+
         return new self(
             $data['name'],
             $data['inputSchema'],
             isset($data['description']) && \is_string($data['description']) ? $data['description'] : null,
             isset($data['annotations']) && \is_array($data['annotations']) ? ToolAnnotations::fromArray($data['annotations']) : null,
             isset($data['icons']) && \is_array($data['icons']) ? array_map(Icon::fromArray(...), $data['icons']) : null,
-            isset($data['_meta']) && \is_array($data['_meta']) ? $data['_meta'] : null
+            isset($data['_meta']) && \is_array($data['_meta']) ? $data['_meta'] : null,
+            isset($data['outputSchema']) && \is_array($data['outputSchema']) ? $data['outputSchema'] : null,
         );
     }
 
@@ -95,7 +115,8 @@ public static function fromArray(array $data): self
      *     description?: string,
      *     annotations?: ToolAnnotations,
      *     icons?: Icon[],
-     *     _meta?: array<string, mixed>
+     *     _meta?: array<string, mixed>,
+     *     outputSchema?: ToolOutputSchema
      * }
      */
     public function jsonSerialize(): array
@@ -116,6 +137,9 @@ public function jsonSerialize(): array
         if (null !== $this->meta) {
             $data['_meta'] = $this->meta;
         }
+        if (null !== $this->outputSchema) {
+            $data['outputSchema'] = $this->outputSchema;
+        }
 
         return $data;
     }
diff --git a/src/Server/Builder.php b/src/Server/Builder.php
index 363a09c5..1079c8a4 100644
--- a/src/Server/Builder.php
+++ b/src/Server/Builder.php
@@ -87,7 +87,8 @@ final class Builder
      *     description: ?string,
      *     annotations: ?ToolAnnotations,
      *     icons: ?Icon[],
-     *     meta: ?array<string, mixed>
+     *     meta: ?array<string, mixed>,
+     *     outputSchema: ?array<string, mixed>,
      * }[]
      */
     private array $tools = [];
@@ -330,6 +331,7 @@ public function setProtocolVersion(ProtocolVersion $protocolVersion): self
      * @param array<string, mixed>|null $inputSchema
      * @param ?Icon[]                   $icons
      * @param array<string, mixed>|null $meta
+     * @param array<string, mixed>|null $outputSchema
      */
     public function addTool(
         callable|array|string $handler,
@@ -339,6 +341,7 @@ public function addTool(
         ?array $inputSchema = null,
         ?array $icons = null,
         ?array $meta = null,
+        ?array $outputSchema = null,
     ): self {
         $this->tools[] = compact(
             'handler',
@@ -348,6 +351,7 @@ public function addTool(
             'inputSchema',
             'icons',
             'meta',
+            'outputSchema',
         );
 
         return $this;
diff --git a/src/Server/Handler/Request/CallToolHandler.php b/src/Server/Handler/Request/CallToolHandler.php
index 13a4b536..c19b5b8c 100644
--- a/src/Server/Handler/Request/CallToolHandler.php
+++ b/src/Server/Handler/Request/CallToolHandler.php
@@ -65,13 +65,16 @@ public function handle(Request $request, SessionInterface $session): Response|Er
 
             $result = $this->referenceHandler->handle($reference, $arguments);
 
+            $structuredContent = null;
             if (!$result instanceof CallToolResult) {
-                $result = new CallToolResult($reference->formatResult($result));
+                $structuredContent = $reference->extractStructuredContent($result);
+                $result = new CallToolResult($reference->formatResult($result), structuredContent: $structuredContent);
             }
 
             $this->logger->debug('Tool executed successfully', [
                 'name' => $toolName,
                 'result_type' => \gettype($result),
+                'structured_content' => $structuredContent,
             ]);
 
             return new Response($request->getId(), $result);
diff --git a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_all_day_reminder.json b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_all_day_reminder.json
index 1e7667fa..5f6e553f 100644
--- a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_all_day_reminder.json
+++ b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_all_day_reminder.json
@@ -5,5 +5,18 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Event \\\"Project Deadline\\\" scheduled successfully for \\\"2024-12-15\\\".\",\n    \"event_details\": {\n        \"title\": \"Project Deadline\",\n        \"date\": \"2024-12-15\",\n        \"type\": \"reminder\",\n        \"time\": \"All day\",\n        \"priority\": \"Normal\",\n        \"attendees\": [],\n        \"invites_will_be_sent\": false\n    }\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Event \"Project Deadline\" scheduled successfully for \"2024-12-15\".",
+    "event_details": {
+      "title": "Project Deadline",
+      "date": "2024-12-15",
+      "type": "reminder",
+      "time": "All day",
+      "priority": "Normal",
+      "attendees": [],
+      "invites_will_be_sent": false
+    }
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_high_priority.json b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_high_priority.json
index 5309d2e9..8a702475 100644
--- a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_high_priority.json
+++ b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_high_priority.json
@@ -5,5 +5,20 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Event \\\"Client Call\\\" scheduled successfully for \\\"2024-12-02\\\".\",\n    \"event_details\": {\n        \"title\": \"Client Call\",\n        \"date\": \"2024-12-02\",\n        \"type\": \"call\",\n        \"time\": \"14:30\",\n        \"priority\": \"Normal\",\n        \"attendees\": [\n            \"client@example.com\"\n        ],\n        \"invites_will_be_sent\": false\n    }\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Event \"Client Call\" scheduled successfully for \"2024-12-02\".",
+    "event_details": {
+      "title": "Client Call",
+      "date": "2024-12-02",
+      "type": "call",
+      "time": "14:30",
+      "priority": "Normal",
+      "attendees": [
+        "client@example.com"
+      ],
+      "invites_will_be_sent": false
+    }
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_low_priority.json b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_low_priority.json
index a9f4d35f..97c2340e 100644
--- a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_low_priority.json
+++ b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_low_priority.json
@@ -5,5 +5,20 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Event \\\"Office Party\\\" scheduled successfully for \\\"2024-12-20\\\".\",\n    \"event_details\": {\n        \"title\": \"Office Party\",\n        \"date\": \"2024-12-20\",\n        \"type\": \"other\",\n        \"time\": \"18:00\",\n        \"priority\": \"Normal\",\n        \"attendees\": [\n            \"team@company.com\"\n        ],\n        \"invites_will_be_sent\": true\n    }\n}"
     }
   ],
+  "structuredContent": {
+  "success": true,
+  "message": "Event \"Office Party\" scheduled successfully for \"2024-12-20\".",
+  "event_details": {
+    "title": "Office Party",
+    "date": "2024-12-20",
+    "type": "other",
+    "time": "18:00",
+    "priority": "Normal",
+    "attendees": [
+      "team@company.com"
+    ],
+    "invites_will_be_sent": true
+    }
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_meeting_with_time.json b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_meeting_with_time.json
index 68c6f014..cf9d7b1d 100644
--- a/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_meeting_with_time.json
+++ b/tests/Inspector/Http/snapshots/HttpComplexToolSchemaTest-tools_call-schedule_event_meeting_with_time.json
@@ -5,5 +5,21 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Event \\\"Team Standup\\\" scheduled successfully for \\\"2024-12-01\\\".\",\n    \"event_details\": {\n        \"title\": \"Team Standup\",\n        \"date\": \"2024-12-01\",\n        \"type\": \"meeting\",\n        \"time\": \"09:00\",\n        \"priority\": \"Normal\",\n        \"attendees\": [\n            \"alice@example.com\",\n            \"bob@example.com\"\n        ],\n        \"invites_will_be_sent\": true\n    }\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Event \"Team Standup\" scheduled successfully for \"2024-12-01\".",
+    "event_details": {
+      "title": "Team Standup",
+      "date": "2024-12-01",
+      "type": "meeting",
+      "time": "09:00",
+      "priority": "Normal",
+      "attendees": [
+      "alice@example.com",
+      "bob@example.com"
+      ],
+      "invites_will_be_sent": true
+    }
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-send_welcome.json b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-send_welcome.json
index 95ed1898..29908263 100644
--- a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-send_welcome.json
+++ b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-send_welcome.json
@@ -5,5 +5,9 @@
       "text": "{\n    \"success\": true,\n    \"message_sent\": \"Welcome, Alice! Welcome to our platform!\"\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message_sent": "Welcome, Alice! Welcome to our platform!"
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-test_tool_without_params.json b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-test_tool_without_params.json
index cac9850a..d680ebab 100644
--- a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-test_tool_without_params.json
+++ b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-test_tool_without_params.json
@@ -5,5 +5,9 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Test tool without params\"\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Test tool without params"
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-calculate_range.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-calculate_range.json
index 817d33d9..d21488a0 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-calculate_range.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-calculate_range.json
@@ -5,5 +5,11 @@
             "text": "{\n    \"result\": 50,\n    \"operation\": \"10 multiply 5\",\n    \"precision\": 2,\n    \"within_bounds\": true\n}"
         }
     ],
+    "structuredContent": {
+        "result": 50,
+        "operation": "10 multiply 5",
+        "precision": 2,
+        "within_bounds": true
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-format_text.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-format_text.json
index eb9d89de..c14b72a5 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-format_text.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-format_text.json
@@ -5,5 +5,11 @@
             "text": "{\n    \"original\": \"Hello World Test\",\n    \"formatted\": \"HELLO WORLD TEST\",\n    \"length\": 16,\n    \"format_applied\": \"uppercase\"\n}"
         }
     ],
+    "structuredContent": {
+        "original": "Hello World Test",
+        "formatted": "HELLO WORLD TEST",
+        "length": 16,
+        "format_applied": "uppercase"
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-generate_config.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-generate_config.json
index e193e9fb..37b4540a 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-generate_config.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-generate_config.json
@@ -5,5 +5,30 @@
             "text": "{\n    \"success\": true,\n    \"config\": {\n        \"app\": {\n            \"name\": \"TestApp\",\n            \"env\": \"development\",\n            \"debug\": true,\n            \"url\": \"https://example.com\",\n            \"port\": 8080\n        },\n        \"generated_at\": \"2025-01-01T00:00:00+00:00\",\n        \"version\": \"1.0.0\",\n        \"features\": {\n            \"logging\": true,\n            \"caching\": false,\n            \"analytics\": false,\n            \"rate_limiting\": false\n        }\n    },\n    \"validation\": {\n        \"app_name_valid\": true,\n        \"url_valid\": true,\n        \"port_in_range\": true\n    }\n}"
         }
     ],
+    "structuredContent": {
+        "success": true,
+        "config": {
+            "app": {
+                "name": "TestApp",
+                "env": "development",
+                "debug": true,
+                "url": "https://example.com",
+                "port": 8080
+            },
+            "generated_at": "2025-01-01T00:00:00+00:00",
+            "version": "1.0.0",
+            "features": {
+                "logging": true,
+                "caching": false,
+                "analytics": false,
+                "rate_limiting": false
+            }
+        },
+        "validation": {
+            "app_name_valid": true,
+            "url_valid": true,
+            "port_in_range": true
+        }
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-manage_list.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-manage_list.json
index 25623f28..18c414ec 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-manage_list.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-manage_list.json
@@ -5,5 +5,27 @@
             "text": "{\n    \"original_count\": 4,\n    \"processed_count\": 4,\n    \"action\": \"sort\",\n    \"original\": [\n        \"apple\",\n        \"banana\",\n        \"cherry\",\n        \"date\"\n    ],\n    \"processed\": [\n        \"apple\",\n        \"banana\",\n        \"cherry\",\n        \"date\"\n    ],\n    \"stats\": {\n        \"average_length\": 5.25,\n        \"shortest\": 4,\n        \"longest\": 6\n    }\n}"
         }
     ],
+    "structuredContent": {
+        "original_count": 4,
+        "processed_count": 4,
+        "action": "sort",
+        "original": [
+            "apple",
+            "banana",
+            "cherry",
+            "date"
+        ],
+        "processed": [
+            "apple",
+            "banana",
+            "cherry",
+            "date"
+        ],
+        "stats": {
+        "average_length": 5.25,
+        "shortest": 4,
+        "longest": 6
+        }
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-schedule_event.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-schedule_event.json
index 924527dc..f597105d 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-schedule_event.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-schedule_event.json
@@ -5,5 +5,27 @@
             "text": "{\n    \"success\": true,\n    \"event\": {\n        \"id\": \"event_test123456789\",\n        \"title\": \"Team Meeting\",\n        \"start_time\": \"2025-01-01T00:00:00+00:00\",\n        \"end_time\": \"2025-01-01T00:00:00+00:00\",\n        \"duration_hours\": 1.5,\n        \"priority\": \"high\",\n        \"attendees\": [\n            \"alice@example.com\",\n            \"bob@example.com\"\n        ],\n        \"created_at\": \"2025-01-01T00:00:00+00:00\"\n    },\n    \"info\": {\n        \"attendee_count\": 2,\n        \"is_all_day\": false,\n        \"is_future\": false,\n        \"timezone_note\": \"Times are in UTC\"\n    }\n}"
         }
     ],
+    "structuredContent": {
+        "success": true,
+        "event": {
+            "id": "event_test123456789",
+            "title": "Team Meeting",
+            "start_time": "2025-01-01T00:00:00+00:00",
+            "end_time": "2025-01-01T00:00:00+00:00",
+            "duration_hours": 1.5,
+            "priority": "high",
+            "attendees": [
+                "alice@example.com",
+                "bob@example.com"
+            ],
+            "created_at": "2025-01-01T00:00:00+00:00"
+        },
+        "info": {
+            "attendee_count": 2,
+            "is_all_day": false,
+            "is_future": false,
+            "timezone_note": "Times are in UTC"
+        }
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-validate_profile.json b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-validate_profile.json
index 9fe2fa53..e87f6cbe 100644
--- a/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-validate_profile.json
+++ b/tests/Inspector/Http/snapshots/HttpSchemaShowcaseTest-tools_call-validate_profile.json
@@ -5,5 +5,17 @@
             "text": "{\n    \"valid\": true,\n    \"profile\": {\n        \"name\": \"John Doe\",\n        \"email\": \"john@example.com\",\n        \"age\": 30,\n        \"role\": \"user\"\n    },\n    \"errors\": [],\n    \"warnings\": [],\n    \"processed_at\": \"2025-01-01 00:00:00\"\n}"
         }
     ],
+    "structuredContent": {
+        "valid": true,
+        "profile": {
+            "name": "John Doe",
+            "email": "john@example.com",
+            "age": 30,
+            "role": "user"
+        },
+        "errors": [],
+        "warnings": [],
+        "processed_at": "2025-01-01 00:00:00"
+    },
     "isError": false
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-add_task.json b/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-add_task.json
index 9ded3d2a..193d8b8e 100644
--- a/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-add_task.json
+++ b/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-add_task.json
@@ -5,5 +5,12 @@
       "text": "{\n    \"id\": 4,\n    \"userId\": \"alice\",\n    \"description\": \"Complete the project documentation\",\n    \"completed\": false,\n    \"createdAt\": \"2025-01-01T00:00:00+00:00\"\n}"
     }
   ],
+  "structuredContent": {
+    "id": 4,
+    "userId": "alice",
+    "description": "Complete the project documentation",
+    "completed": false,
+    "createdAt": "2025-01-01T00:00:00+00:00"
+  },
   "isError": false
-}
+}
\ No newline at end of file
diff --git a/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-complete_task.json b/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-complete_task.json
index 3d852eda..3e17038b 100644
--- a/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-complete_task.json
+++ b/tests/Inspector/Stdio/snapshots/StdioCustomDependenciesTest-tools_call-complete_task.json
@@ -5,5 +5,9 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Task 1 completed.\"\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Task 1 completed."
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call-update_setting.json b/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call-update_setting.json
index 37b42155..51786523 100644
--- a/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call-update_setting.json
+++ b/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call-update_setting.json
@@ -5,5 +5,9 @@
       "text": "{\n    \"success\": true,\n    \"message\": \"Precision updated to 3.\"\n}"
     }
   ],
+  "structuredContent": {
+    "success": true,
+    "message": "Precision updated to 3."
+  },
   "isError": false
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call.json b/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call.json
index a73c8b94..bdfec0c0 100644
--- a/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call.json
+++ b/tests/Inspector/Stdio/snapshots/StdioDiscoveryCalculatorTest-tools_call.json
@@ -5,5 +5,8 @@
       "text": "19.8"
     }
   ],
-  "isError": false
+  "isError": false,
+  "structuredContent": {
+    "result": 19.8
+  }
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_debug.json b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_debug.json
index 3b11d407..b046832e 100644
--- a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_debug.json
+++ b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_debug.json
@@ -5,5 +5,10 @@
       "text": "{\n    \"mode\": \"debug\",\n    \"processed_input\": \"DEBUG TEST\",\n    \"message\": \"Processed in DEBUG mode.\"\n}"
     }
   ],
-  "isError": false
+  "isError": false,
+  "structuredContent": {
+    "mode": "debug",
+    "processed_input": "DEBUG TEST",
+    "message": "Processed in DEBUG mode."
+  }
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_default.json b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_default.json
index fde189ee..af00a82b 100644
--- a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_default.json
+++ b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_default.json
@@ -5,5 +5,10 @@
       "text": "{\n    \"mode\": \"default\",\n    \"original_input\": \"test data\",\n    \"message\": \"Processed in default mode (APP_MODE not recognized or not set).\"\n}"
     }
   ],
-  "isError": false
+  "isError": false,
+  "structuredContent": {
+    "mode": "default",
+    "original_input": "test data",
+    "message": "Processed in default mode (APP_MODE not recognized or not set)."
+  }
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_production.json b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_production.json
index dd4cd9dc..4f30f8a0 100644
--- a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_production.json
+++ b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_call-process_data_production.json
@@ -5,5 +5,10 @@
       "text": "{\n    \"mode\": \"production\",\n    \"processed_input_length\": 15,\n    \"message\": \"Processed in PRODUCTION mode (summary only).\"\n}"
     }
   ],
-  "isError": false
+  "isError": false,
+  "structuredContent": {
+    "mode": "production",
+    "processed_input_length": 15,
+    "message": "Processed in PRODUCTION mode (summary only)."
+  }
 }
diff --git a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_list.json b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_list.json
index 32141675..f5d19c41 100644
--- a/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_list.json
+++ b/tests/Inspector/Stdio/snapshots/StdioEnvVariablesTest-tools_list.json
@@ -14,6 +14,31 @@
         "required": [
           "input"
         ]
+      },
+      "outputSchema": {
+        "type": "object",
+        "properties": {
+          "mode": {
+            "type": "string",
+            "description": "The processing mode used"
+          },
+          "processed_input": {
+            "type": "string",
+            "description": "The processed input data"
+          },
+          "original_input": {
+            "type": "string",
+            "description": "The original input data (only in default mode)"
+          },
+          "message": {
+            "type": "string",
+            "description": "A descriptive message about the processing"
+          }
+        },
+        "required": [
+          "mode",
+          "message"
+        ]
       }
     }
   ]
diff --git a/tests/Unit/Capability/Attribute/McpToolTest.php b/tests/Unit/Capability/Attribute/McpToolTest.php
index e2814af7..b6ab86d5 100644
--- a/tests/Unit/Capability/Attribute/McpToolTest.php
+++ b/tests/Unit/Capability/Attribute/McpToolTest.php
@@ -30,14 +30,15 @@ public function testInstantiatesWithCorrectProperties(): void
         $this->assertSame($description, $attribute->description);
     }
 
-    public function testInstantiatesWithNullValuesForNameAndDescription(): void
+    public function testInstantiatesWithNullValuesForNameDescriptionAndOutputSchema(): void
     {
         // Arrange & Act
-        $attribute = new McpTool(name: null, description: null);
+        $attribute = new McpTool(name: null, description: null, outputSchema: null);
 
         // Assert
         $this->assertNull($attribute->name);
         $this->assertNull($attribute->description);
+        $this->assertNull($attribute->outputSchema);
     }
 
     public function testInstantiatesWithMissingOptionalArguments(): void
@@ -48,5 +49,31 @@ public function testInstantiatesWithMissingOptionalArguments(): void
         // Assert
         $this->assertNull($attribute->name);
         $this->assertNull($attribute->description);
+        $this->assertNull($attribute->outputSchema);
+    }
+
+    public function testInstantiatesWithOutputSchema(): void
+    {
+        // Arrange
+        $name = 'test-tool-name';
+        $description = 'This is a test description.';
+        $outputSchema = [
+            'type' => 'object',
+            'properties' => [
+                'result' => [
+                    'type' => 'string',
+                    'description' => 'The result of the operation',
+                ],
+            ],
+            'required' => ['result'],
+        ];
+
+        // Act
+        $attribute = new McpTool(name: $name, description: $description, outputSchema: $outputSchema);
+
+        // Assert
+        $this->assertSame($name, $attribute->name);
+        $this->assertSame($description, $attribute->description);
+        $this->assertSame($outputSchema, $attribute->outputSchema);
     }
 }
diff --git a/tests/Unit/Capability/Discovery/DocBlockParserTest.php b/tests/Unit/Capability/Discovery/DocBlockParserTest.php
index b8501b28..df914755 100644
--- a/tests/Unit/Capability/Discovery/DocBlockParserTest.php
+++ b/tests/Unit/Capability/Discovery/DocBlockParserTest.php
@@ -16,7 +16,6 @@
 use phpDocumentor\Reflection\DocBlock\Tags\Deprecated;
 use phpDocumentor\Reflection\DocBlock\Tags\Param;
 use phpDocumentor\Reflection\DocBlock\Tags\See;
-use phpDocumentor\Reflection\DocBlock\Tags\Throws;
 use PHPUnit\Framework\TestCase;
 
 class DocBlockParserTest extends TestCase
@@ -109,12 +108,6 @@ public function testGetTagsByNameReturnsSpecificTags()
 
         $this->assertInstanceOf(DocBlock::class, $docBlock);
 
-        $throwsTags = $docBlock->getTagsByName('throws');
-        $this->assertCount(1, $throwsTags);
-        $this->assertInstanceOf(Throws::class, $throwsTags[0]);
-        $this->assertEquals('\\RuntimeException', (string) $throwsTags[0]->getType());
-        $this->assertEquals('if processing fails', $throwsTags[0]->getDescription()->render());
-
         $deprecatedTags = $docBlock->getTagsByName('deprecated');
         $this->assertCount(1, $deprecatedTags);
         $this->assertInstanceOf(Deprecated::class, $deprecatedTags[0]);
diff --git a/tests/Unit/Capability/Discovery/DocBlockTestFixture.php b/tests/Unit/Capability/Discovery/DocBlockTestFixture.php
index a218ad63..7a753ddf 100644
--- a/tests/Unit/Capability/Discovery/DocBlockTestFixture.php
+++ b/tests/Unit/Capability/Discovery/DocBlockTestFixture.php
@@ -70,8 +70,6 @@ public function methodWithReturn(): string
      *
      * @return bool status of the operation
      *
-     * @throws \RuntimeException if processing fails
-     *
      * @deprecated use newMethod() instead
      * @see DocBlockTestFixture::newMethod()
      */
diff --git a/tests/Unit/Capability/Discovery/SchemaGeneratorFixture.php b/tests/Unit/Capability/Discovery/SchemaGeneratorFixture.php
index 786342e8..0d40026c 100644
--- a/tests/Unit/Capability/Discovery/SchemaGeneratorFixture.php
+++ b/tests/Unit/Capability/Discovery/SchemaGeneratorFixture.php
@@ -11,6 +11,7 @@
 
 namespace Mcp\Tests\Unit\Capability\Discovery;
 
+use Mcp\Capability\Attribute\McpTool;
 use Mcp\Capability\Attribute\Schema;
 use Mcp\Tests\Unit\Fixtures\Enum\BackedIntEnum;
 use Mcp\Tests\Unit\Fixtures\Enum\BackedStringEnum;
@@ -337,6 +338,12 @@ public function mixedTypes(
     /**
      * Complex nested Schema constraints.
      */
+    #[McpTool(
+        outputSchema: [
+            'type' => 'object',
+            'additionalProperties' => true,
+        ]
+    )]
     public function complexNestedSchema(
         #[Schema(
             type: 'object',
@@ -399,6 +406,12 @@ public function typePrecedenceTest(
      * Method with no parameters but Schema description.
      */
     #[Schema(description: 'Gets server status. Takes no arguments.', properties: [])]
+    #[McpTool(
+        outputSchema: [
+            'type' => 'object',
+            'additionalProperties' => true,
+        ]
+    )]
     public function noParamsWithSchema(): array
     {
         return ['status' => 'OK'];
@@ -424,4 +437,20 @@ public function withParameterNamedSessionWithWeirdCase(string $_sesSion): void
     public function withParameterNamedRequest(string $_request): void
     {
     }
+
+    // ===== OUTPUT SCHEMA FIXTURES =====
+    #[McpTool(
+        outputSchema: [
+            'type' => 'object',
+            'properties' => [
+                'message' => ['type' => 'string'],
+            ],
+            'required' => ['message'],
+            'description' => 'The result of the operation',
+        ]
+    )]
+    public function returnWithExplicitOutputSchema(): array
+    {
+        return ['message' => 'result'];
+    }
 }
diff --git a/tests/Unit/Capability/Discovery/SchemaGeneratorTest.php b/tests/Unit/Capability/Discovery/SchemaGeneratorTest.php
index e9e37f6f..5089e7d7 100644
--- a/tests/Unit/Capability/Discovery/SchemaGeneratorTest.php
+++ b/tests/Unit/Capability/Discovery/SchemaGeneratorTest.php
@@ -346,4 +346,45 @@ public function testGenerateWithForbiddenParameterNames(string $methodName)
         $this->expectException(InvalidArgumentException::class);
         $this->schemaGenerator->generate($method);
     }
+
+    public function testGenerateOutputSchemaReturnsNullForVoidReturnType(): void
+    {
+        $method = new \ReflectionMethod(SchemaGeneratorFixture::class, 'noParams');
+        $schema = $this->schemaGenerator->generateOutputSchema($method);
+        $this->assertNull($schema);
+    }
+
+    public function testGenerateOutputSchemaWithReturnDescription(): void
+    {
+        $method = new \ReflectionMethod(SchemaGeneratorFixture::class, 'returnWithExplicitOutputSchema');
+        $schema = $this->schemaGenerator->generateOutputSchema($method);
+        $this->assertEquals([
+            'type' => 'object',
+            'properties' => [
+                'message' => ['type' => 'string'],
+            ],
+            'required' => ['message'],
+            'description' => 'The result of the operation',
+        ], $schema);
+    }
+
+    public function testGenerateOutputSchemaForArrayReturnType(): void
+    {
+        $method = new \ReflectionMethod(SchemaGeneratorFixture::class, 'noParamsWithSchema');
+        $schema = $this->schemaGenerator->generateOutputSchema($method);
+        $this->assertEquals([
+            'type' => 'object',
+            'additionalProperties' => true,
+        ], $schema);
+    }
+
+    public function testGenerateOutputSchemaForComplexNestedSchema(): void
+    {
+        $method = new \ReflectionMethod(SchemaGeneratorFixture::class, 'complexNestedSchema');
+        $schema = $this->schemaGenerator->generateOutputSchema($method);
+        $this->assertEquals([
+            'type' => 'object',
+            'additionalProperties' => true,
+        ], $schema);
+    }
 }
diff --git a/tests/Unit/Capability/RegistryTest.php b/tests/Unit/Capability/RegistryTest.php
index d97ccf41..c5c3230c 100644
--- a/tests/Unit/Capability/RegistryTest.php
+++ b/tests/Unit/Capability/RegistryTest.php
@@ -527,7 +527,91 @@ public function testMultipleRegistrationsOfSameElementWithSameType(): void
         $this->assertEquals('second', ($toolRef->handler)());
     }
 
-    private function createValidTool(string $name): Tool
+    public function testExtractStructuredContentReturnsNullWhenOutputSchemaIsNull(): void
+    {
+        $tool = $this->createValidTool('test_tool', null);
+        $this->registry->registerTool($tool, fn () => 'result');
+
+        $toolRef = $this->registry->getTool('test_tool');
+        $this->assertNull($toolRef->extractStructuredContent('result'));
+    }
+
+    public function testExtractStructuredContentReturnsArrayMatchingSchema(): void
+    {
+        $tool = $this->createValidTool('test_tool', [
+            'type' => 'object',
+            'properties' => [
+                'param' => ['type' => 'string'],
+            ],
+            'required' => ['param'],
+        ]);
+        $this->registry->registerTool($tool, fn () => [
+            'param' => 'test',
+        ]);
+
+        $toolRef = $this->registry->getTool('test_tool');
+        $this->assertEquals([
+            'param' => 'test',
+        ], $toolRef->extractStructuredContent([
+            'param' => 'test',
+        ]));
+    }
+
+    public function testExtractStructuredContentReturnsArrayDirectlyForAdditionalProperties(): void
+    {
+        $tool = $this->createValidTool('test_tool', [
+            'type' => 'object',
+            'additionalProperties' => true,
+        ]);
+        $this->registry->registerTool($tool, fn () => ['success' => true, 'message' => 'done']);
+
+        $toolRef = $this->registry->getTool('test_tool');
+        $this->assertEquals(['success' => true, 'message' => 'done'], $toolRef->extractStructuredContent(['success' => true, 'message' => 'done']));
+    }
+
+    public function testExtractStructuredContentReturnsArrayDirectlyForArrayOutputSchema(): void
+    {
+        // Arrange
+        $outputSchema = [
+            'type' => 'array',
+            'items' => [
+                'type' => 'object',
+                'properties' => [
+                    'foo' => [
+                        'type' => 'string',
+                        'description' => 'A static value',
+                    ],
+                ],
+                'required' => ['foo'],
+            ],
+        ];
+
+        $tool = $this->createValidTool('list_static_data', $outputSchema);
+        $toolReturnValue = [
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+        ];
+
+        $this->registry->registerTool($tool, fn () => $toolReturnValue);
+
+        // Act
+        $toolRef = $this->registry->getTool('list_static_data');
+        $structuredContent = $toolRef->extractStructuredContent($toolReturnValue);
+
+        // Assert
+        $this->assertNotNull($structuredContent);
+        $this->assertCount(4, $structuredContent);
+        $this->assertEquals([
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+            ['foo' => 'bar'],
+        ], $structuredContent);
+    }
+
+    private function createValidTool(string $name, ?array $outputSchema = null): Tool
     {
         return new Tool(
             name: $name,
@@ -540,6 +624,9 @@ private function createValidTool(string $name): Tool
             ],
             description: "Test tool: {$name}",
             annotations: null,
+            icons: null,
+            meta: null,
+            outputSchema: $outputSchema
         );
     }
 
diff --git a/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php b/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
index eb2f2ab6..90af0c84 100644
--- a/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
+++ b/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
@@ -21,6 +21,7 @@
 use Mcp\Schema\JsonRpc\Response;
 use Mcp\Schema\Request\CallToolRequest;
 use Mcp\Schema\Result\CallToolResult;
+use Mcp\Schema\Tool;
 use Mcp\Server\Handler\Request\CallToolHandler;
 use Mcp\Server\Session\SessionInterface;
 use PHPUnit\Framework\MockObject\MockObject;
@@ -59,7 +60,9 @@ public function testSupportsCallToolRequest(): void
     public function testHandleSuccessfulToolCall(): void
     {
         $request = $this->createCallToolRequest('greet_user', ['name' => 'John']);
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $expectedResult = new CallToolResult([new TextContent('Hello, John!')]);
 
         $this->registry
@@ -92,7 +95,9 @@ public function testHandleSuccessfulToolCall(): void
     public function testHandleToolCallWithEmptyArguments(): void
     {
         $request = $this->createCallToolRequest('simple_tool', []);
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $expectedResult = new CallToolResult([new TextContent('Simple result')]);
 
         $this->registry
@@ -129,7 +134,9 @@ public function testHandleToolCallWithComplexArguments(): void
             'null_param' => null,
         ];
         $request = $this->createCallToolRequest('complex_tool', $arguments);
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $expectedResult = new CallToolResult([new TextContent('Complex result')]);
 
         $this->registry
@@ -182,7 +189,9 @@ public function testHandleToolCallExceptionReturnsResponseWithErrorResult(): voi
         $request = $this->createCallToolRequest('failing_tool', ['param' => 'value']);
         $exception = new ToolCallException('Tool execution failed');
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -217,7 +226,9 @@ public function testHandleWithNullResult(): void
         $request = $this->createCallToolRequest('null_tool', []);
         $expectedResult = new CallToolResult([]);
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -254,7 +265,9 @@ public function testHandleLogsErrorWithCorrectParameters(): void
         $request = $this->createCallToolRequest('test_tool', ['key1' => 'value1', 'key2' => 42]);
         $exception = new ToolCallException('Custom error message');
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -297,7 +310,9 @@ public function testHandleGenericExceptionReturnsError(): void
         $request = $this->createCallToolRequest('failing_tool', ['param' => 'value']);
         $exception = new \RuntimeException('Internal database connection failed');
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -324,7 +339,10 @@ public function testHandleWithSpecialCharactersInToolName(): void
         $request = $this->createCallToolRequest('tool-with_special.chars', []);
         $expectedResult = new CallToolResult([new TextContent('Special tool result')]);
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
+
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -359,7 +377,9 @@ public function testHandleWithSpecialCharactersInArguments(): void
         $request = $this->createCallToolRequest('unicode_tool', $arguments);
         $expectedResult = new CallToolResult([new TextContent('Unicode handled')]);
 
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $this->registry
             ->expects($this->once())
             ->method('getTool')
@@ -387,7 +407,9 @@ public function testHandleWithSpecialCharactersInArguments(): void
     public function testHandleReturnsStructuredContentResult(): void
     {
         $request = $this->createCallToolRequest('structured_tool', ['query' => 'php']);
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $structuredResult = new CallToolResult([new TextContent('Rendered results')], false, ['result' => 'Rendered results']);
 
         $this->registry
@@ -416,7 +438,9 @@ public function testHandleReturnsStructuredContentResult(): void
     public function testHandleReturnsCallToolResult(): void
     {
         $request = $this->createCallToolRequest('result_tool', ['query' => 'php']);
-        $toolReference = $this->createMock(ToolReference::class);
+        $toolReference = $this->createToolReference('greet_user', function () {
+            return 'Hello, John!';
+        });
         $callToolResult = new CallToolResult([new TextContent('Error result')], true);
 
         $this->registry
@@ -457,4 +481,22 @@ private function createCallToolRequest(string $name, array $arguments): CallTool
             ],
         ]);
     }
+
+    private function createToolReference(
+        string $name,
+        callable $handler,
+        ?array $outputSchema = null,
+        array $methodsToMock = ['formatResult'],
+    ): ToolReference&MockObject {
+        $tool = new Tool($name, ['type' => 'object', 'properties' => [], 'required' => null], null, null, null, null, $outputSchema);
+
+        $builder = $this->getMockBuilder(ToolReference::class)
+            ->setConstructorArgs([$tool, $handler]);
+
+        if (!empty($methodsToMock)) {
+            $builder->onlyMethods($methodsToMock);
+        }
+
+        return $builder->getMock();
+    }
 }