diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01bf9a90..3e8fd215 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 All notable changes to `mcp/sdk` will be documented in this file.
 
+0.8.0
+-----
+
+* Add `Mcp\Schema\Content\ResourceLink` for the spec's `resource_link` content block (protocol revision 2025-06-18+), letting tool results and prompt messages reference a resource by URI/name without embedding its contents. Accepted anywhere `resource` (`EmbeddedResource`) content is (de)serialized: `CallToolResult::fromArray()`, `PromptMessage::fromArray()`, and `PromptResultFormatter`.
+
 0.7.0
 -----
 
diff --git a/docs/mcp-elements.md b/docs/mcp-elements.md
index 0f8c9eb2..3617a2fc 100644
--- a/docs/mcp-elements.md
+++ b/docs/mcp-elements.md
@@ -107,7 +107,7 @@ public function returnVoid(): void { /* no return */ }           // Empty conten
 For fine control over output formatting:
 
 ```php
-use Mcp\Schema\Content\{TextContent, ImageContent, AudioContent, EmbeddedResource};
+use Mcp\Schema\Content\{TextContent, ImageContent, AudioContent, ResourceLink, EmbeddedResource};
 
 public function getFormattedCode(): TextContent
 {
@@ -142,6 +142,17 @@ public function getEmbeddedResource(): EmbeddedResource
         resource: ['uri' => 'file://data.json', 'text' => 'File content']
     );
 }
+
+public function getResourceLink(): ResourceLink
+{
+    // Reference a resource by URI without embedding its contents, e.g. when
+    // a tool result would otherwise need to inline many or large resources.
+    return new ResourceLink(
+        uri: 'file://data.json',
+        name: 'data.json',
+        mimeType: 'application/json'
+    );
+}
 ```
 
 #### Multiple Content Items
diff --git a/examples/server/discovery-userprofile/McpElements.php b/examples/server/discovery-userprofile/McpElements.php
index 8ab6c7d4..c8532544 100644
--- a/examples/server/discovery-userprofile/McpElements.php
+++ b/examples/server/discovery-userprofile/McpElements.php
@@ -18,6 +18,9 @@
 use Mcp\Capability\Attribute\McpTool;
 use Mcp\Exception\PromptGetException;
 use Mcp\Exception\ResourceReadException;
+use Mcp\Schema\Content\Content;
+use Mcp\Schema\Content\ResourceLink;
+use Mcp\Schema\Content\TextContent;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -87,6 +90,44 @@ public function listUserIds(): array
         return array_keys($this->users);
     }
 
+    /**
+     * Looks up a user and returns a reference to their profile resource.
+     *
+     * Rather than embedding the full profile (as `resources/read` on
+     * `user://{userId}/profile` would), this returns a `resource_link` block
+     * pointing at that resource template so the caller can fetch it
+     * separately if needed. This mirrors how a tool like a search returning
+     * many hits would reference each matching resource by URI instead of
+     * inlining every one of them.
+     *
+     * @param string $userId the ID of the user to look up
+     *
+     * @return Content[] a short summary plus a resource_link to the user's profile
+     */
+    #[McpTool(name: 'lookup_user')]
+    public function lookupUser(
+        #[CompletionProvider(values: ['101', '102', '103'])]
+        string $userId,
+    ): array {
+        $this->logger->info('Executing tool: lookup_user', ['userId' => $userId]);
+
+        if (!isset($this->users[$userId])) {
+            return [new TextContent("User ID {$userId} not found.")];
+        }
+
+        $user = $this->users[$userId];
+
+        return [
+            new TextContent("Found user {$user['name']} ({$user['role']})."),
+            new ResourceLink(
+                uri: "user://{$userId}/profile",
+                name: 'user_profile',
+                description: "Full profile for {$user['name']}.",
+                mimeType: 'application/json',
+            ),
+        ];
+    }
+
     /**
      * Sends a welcome message to a user.
      * (This is a placeholder - in a real app, it might queue an email).
diff --git a/src/Capability/Formatter/PromptResultFormatter.php b/src/Capability/Formatter/PromptResultFormatter.php
index 871bded7..b1a8ba48 100644
--- a/src/Capability/Formatter/PromptResultFormatter.php
+++ b/src/Capability/Formatter/PromptResultFormatter.php
@@ -18,6 +18,7 @@
 use Mcp\Schema\Content\EmbeddedResource;
 use Mcp\Schema\Content\ImageContent;
 use Mcp\Schema\Content\PromptMessage;
+use Mcp\Schema\Content\ResourceLink;
 use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\Content\TextResourceContents;
 use Mcp\Schema\Enum\Role;
@@ -142,18 +143,19 @@ private function formatMessage(mixed $message, ?int $index = null): PromptMessag
     /**
      * Formats content into a proper Content object.
      */
-    private function formatContent(mixed $content, ?int $index = null): TextContent|ImageContent|AudioContent|EmbeddedResource
+    private function formatContent(mixed $content, ?int $index = null): TextContent|ImageContent|AudioContent|ResourceLink|EmbeddedResource
     {
         $indexStr = null !== $index ? " at index {$index}" : '';
 
         if ($content instanceof Content) {
             if (
                 $content instanceof TextContent || $content instanceof ImageContent
-                || $content instanceof AudioContent || $content instanceof EmbeddedResource
+                || $content instanceof AudioContent || $content instanceof ResourceLink
+                || $content instanceof EmbeddedResource
             ) {
                 return $content;
             }
-            throw new RuntimeException("Invalid Content type{$indexStr}. PromptMessage only supports TextContent, ImageContent, AudioContent, or EmbeddedResource.");
+            throw new RuntimeException("Invalid Content type{$indexStr}. PromptMessage only supports TextContent, ImageContent, AudioContent, ResourceLink, or EmbeddedResource.");
         }
 
         if (\is_string($content)) {
@@ -180,7 +182,7 @@ private function formatContent(mixed $content, ?int $index = null): TextContent|
      *
      * @param array<string, mixed> $content
      */
-    private function formatTypedContent(array $content, ?int $index = null): TextContent|ImageContent|AudioContent|EmbeddedResource
+    private function formatTypedContent(array $content, ?int $index = null): TextContent|ImageContent|AudioContent|ResourceLink|EmbeddedResource
     {
         $indexStr = null !== $index ? " at index {$index}" : '';
         $type = $content['type'];
@@ -190,6 +192,7 @@ private function formatTypedContent(array $content, ?int $index = null): TextCon
             'image' => $this->formatImageContent($content, $indexStr),
             'audio' => $this->formatAudioContent($content, $indexStr),
             'resource' => $this->formatResourceContent($content, $indexStr),
+            'resource_link' => $this->formatResourceLinkContent($content, $indexStr),
             default => throw new RuntimeException("Invalid content type '{$type}'{$indexStr}."),
         };
     }
@@ -264,4 +267,19 @@ private function formatResourceContent(array $content, string $indexStr): Embedd
 
         return new EmbeddedResource($resourceObj);
     }
+
+    /**
+     * @param array<string, mixed> $content
+     */
+    private function formatResourceLinkContent(array $content, string $indexStr): ResourceLink
+    {
+        if (!isset($content['uri']) || !\is_string($content['uri'])) {
+            throw new RuntimeException("Invalid 'resource_link' content{$indexStr}: Missing or invalid 'uri' string.");
+        }
+        if (!isset($content['name']) || !\is_string($content['name'])) {
+            throw new RuntimeException("Invalid 'resource_link' content{$indexStr}: Missing or invalid 'name' string.");
+        }
+
+        return new ResourceLink($content['uri'], $content['name']);
+    }
 }
diff --git a/src/Capability/Registry/ToolReference.php b/src/Capability/Registry/ToolReference.php
index 36c0835f..beec1827 100644
--- a/src/Capability/Registry/ToolReference.php
+++ b/src/Capability/Registry/ToolReference.php
@@ -68,6 +68,17 @@ public function formatResult(mixed $toolExecutionResult): array
     public function extractStructuredContent(mixed $toolExecutionResult): ?array
     {
         if (\is_array($toolExecutionResult)) {
+            foreach ($toolExecutionResult as $item) {
+                if ($item instanceof Content) {
+                    // Content items are already reflected in the result's `content`
+                    // array; a raw array holding one or more of them isn't
+                    // structured data and, if it were serialized as-is, could
+                    // produce a `structuredContent` value that isn't a JSON object
+                    // (e.g. a list), which the spec doesn't allow.
+                    return null;
+                }
+            }
+
             return $toolExecutionResult;
         }
 
diff --git a/src/Schema/Content/PromptMessage.php b/src/Schema/Content/PromptMessage.php
index 075d1136..d0b8f769 100644
--- a/src/Schema/Content/PromptMessage.php
+++ b/src/Schema/Content/PromptMessage.php
@@ -20,11 +20,12 @@
  * @phpstan-import-type TextContentData from TextContent
  * @phpstan-import-type ImageContentData from ImageContent
  * @phpstan-import-type AudioContentData from AudioContent
+ * @phpstan-import-type ResourceLinkData from ResourceLink
  * @phpstan-import-type EmbeddedResourceData from EmbeddedResource
  *
  * @phpstan-type PromptMessageData array{
  *     role: string,
- *     content: TextContentData|ImageContentData|AudioContentData|EmbeddedResourceData,
+ *     content: TextContentData|ImageContentData|AudioContentData|ResourceLinkData|EmbeddedResourceData,
  * }
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
@@ -34,12 +35,12 @@ class PromptMessage extends Content
     /**
      * Create a new PromptMessage instance.
      *
-     * @param Role                                                   $role    The role of the message
-     * @param TextContent|ImageContent|AudioContent|EmbeddedResource $content The content of the message
+     * @param Role                                                                $role    The role of the message
+     * @param TextContent|ImageContent|AudioContent|ResourceLink|EmbeddedResource $content The content of the message
      */
     public function __construct(
         public readonly Role $role,
-        public readonly TextContent|ImageContent|AudioContent|EmbeddedResource $content,
+        public readonly TextContent|ImageContent|AudioContent|ResourceLink|EmbeddedResource $content,
     ) {
         parent::__construct('prompt');
     }
@@ -64,6 +65,7 @@ public static function fromArray(array $data): self
             'image' => ImageContent::fromArray($contentData),
             'audio' => AudioContent::fromArray($contentData),
             'resource' => EmbeddedResource::fromArray($contentData),
+            'resource_link' => ResourceLink::fromArray($contentData),
             default => throw new InvalidArgumentException(\sprintf('Invalid content type "%s" for PromptMessage.', $contentType)),
         };
 
@@ -75,7 +77,7 @@ public static function fromArray(array $data): self
      *
      * @return array{
      *     role: string,
-     *     content: TextContent|ImageContent|AudioContent|EmbeddedResource
+     *     content: TextContent|ImageContent|AudioContent|ResourceLink|EmbeddedResource
      * }
      */
     public function jsonSerialize(): array
diff --git a/src/Schema/Content/ResourceLink.php b/src/Schema/Content/ResourceLink.php
new file mode 100644
index 00000000..874cc85a
--- /dev/null
+++ b/src/Schema/Content/ResourceLink.php
@@ -0,0 +1,146 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Schema\Content;
+
+use Mcp\Exception\InvalidArgumentException;
+use Mcp\Schema\Annotations;
+use Mcp\Schema\Icon;
+
+/**
+ * Represents a link to a resource, without embedding its contents.
+ *
+ * A resource that the server is capable of reading, included in a prompt or
+ * tool call result. Unlike `EmbeddedResource`, this points to a resource
+ * without including its full content, allowing clients to fetch it separately.
+ *
+ * @phpstan-import-type AnnotationsData from Annotations
+ * @phpstan-import-type IconData from Icon
+ *
+ * @phpstan-type ResourceLinkData array{
+ *     type: 'resource_link',
+ *     uri: string,
+ *     name: string,
+ *     title?: string,
+ *     description?: string,
+ *     mimeType?: string,
+ *     annotations?: AnnotationsData,
+ *     size?: int,
+ *     icons?: IconData[],
+ *     _meta?: array<string, mixed>,
+ * }
+ *
+ * @author Alex Rothberg <cancan101@users.noreply.github.com>
+ */
+class ResourceLink extends Content
+{
+    /**
+     * @param string                $uri         the URI of this resource
+     * @param string                $name        a short identifier for this resource
+     * @param ?string               $title       optional human-readable title for display in UI
+     * @param ?string               $description a description of what this resource represents. This can be used by clients to improve the LLM's understanding of available resources
+     * @param ?string               $mimeType    the MIME type of this resource, if known
+     * @param ?Annotations          $annotations optional annotations for the client
+     * @param ?int                  $size        the size of the raw resource content, in bytes (before base64 encoding or any tokenization), if known
+     * @param ?Icon[]               $icons       optional icons representing the resource
+     * @param ?array<string, mixed> $meta        optional metadata
+     */
+    public function __construct(
+        public readonly string $uri,
+        public readonly string $name,
+        public readonly ?string $title = null,
+        public readonly ?string $description = null,
+        public readonly ?string $mimeType = null,
+        public readonly ?Annotations $annotations = null,
+        public readonly ?int $size = null,
+        public readonly ?array $icons = null,
+        public readonly ?array $meta = null,
+    ) {
+        parent::__construct('resource_link');
+    }
+
+    /**
+     * @param ResourceLinkData $data
+     */
+    public static function fromArray(array $data): self
+    {
+        if (($data['type'] ?? null) !== 'resource_link') {
+            throw new InvalidArgumentException('Invalid type for ResourceLink.');
+        }
+        if (empty($data['uri']) || !\is_string($data['uri'])) {
+            throw new InvalidArgumentException('Invalid or missing "uri" in ResourceLink data.');
+        }
+        if (empty($data['name']) || !\is_string($data['name'])) {
+            throw new InvalidArgumentException('Invalid or missing "name" in ResourceLink data.');
+        }
+        if (isset($data['_meta']) && !\is_array($data['_meta'])) {
+            throw new InvalidArgumentException('Invalid "_meta" in ResourceLink data.');
+        }
+
+        return new self(
+            uri: $data['uri'],
+            name: $data['name'],
+            title: isset($data['title']) && \is_string($data['title']) ? $data['title'] : null,
+            description: $data['description'] ?? null,
+            mimeType: $data['mimeType'] ?? null,
+            annotations: isset($data['annotations']) ? Annotations::fromArray($data['annotations']) : null,
+            size: isset($data['size']) ? (int) $data['size'] : null,
+            icons: isset($data['icons']) && \is_array($data['icons']) ? array_map(Icon::fromArray(...), $data['icons']) : null,
+            meta: $data['_meta'] ?? null,
+        );
+    }
+
+    /**
+     * @return array{
+     *     type: 'resource_link',
+     *     uri: string,
+     *     name: string,
+     *     title?: string,
+     *     description?: string,
+     *     mimeType?: string,
+     *     annotations?: Annotations,
+     *     size?: int,
+     *     icons?: Icon[],
+     *     _meta?: array<string, mixed>,
+     * }
+     */
+    public function jsonSerialize(): array
+    {
+        $data = [
+            'type' => $this->type,
+            'uri' => $this->uri,
+            'name' => $this->name,
+        ];
+        if (null !== $this->title) {
+            $data['title'] = $this->title;
+        }
+        if (null !== $this->description) {
+            $data['description'] = $this->description;
+        }
+        if (null !== $this->mimeType) {
+            $data['mimeType'] = $this->mimeType;
+        }
+        if (null !== $this->annotations) {
+            $data['annotations'] = $this->annotations;
+        }
+        if (null !== $this->size) {
+            $data['size'] = $this->size;
+        }
+        if (null !== $this->icons) {
+            $data['icons'] = $this->icons;
+        }
+        if (null !== $this->meta) {
+            $data['_meta'] = $this->meta;
+        }
+
+        return $data;
+    }
+}
diff --git a/src/Schema/Result/CallToolResult.php b/src/Schema/Result/CallToolResult.php
index bfbc9fab..e1c41f88 100644
--- a/src/Schema/Result/CallToolResult.php
+++ b/src/Schema/Result/CallToolResult.php
@@ -16,6 +16,7 @@
 use Mcp\Schema\Content\Content;
 use Mcp\Schema\Content\EmbeddedResource;
 use Mcp\Schema\Content\ImageContent;
+use Mcp\Schema\Content\ResourceLink;
 use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\JsonRpc\ResultInterface;
 
@@ -100,6 +101,7 @@ public static function fromArray(array $data): self
                 'image' => ImageContent::fromArray($item),
                 'audio' => AudioContent::fromArray($item),
                 'resource' => EmbeddedResource::fromArray($item),
+                'resource_link' => ResourceLink::fromArray($item),
                 default => throw new InvalidArgumentException(\sprintf('Invalid content type in CallToolResult data: "%s".', $item['type'] ?? null)),
             };
         }
diff --git a/tests/Inspector/Http/HttpDiscoveryUserProfileTest.php b/tests/Inspector/Http/HttpDiscoveryUserProfileTest.php
index 985b01b7..353230a7 100644
--- a/tests/Inspector/Http/HttpDiscoveryUserProfileTest.php
+++ b/tests/Inspector/Http/HttpDiscoveryUserProfileTest.php
@@ -17,6 +17,22 @@ public static function provideMethods(): array
     {
         return [
             ...parent::provideMethods(),
+            'Lookup User Tool' => [
+                'method' => 'tools/call',
+                'options' => [
+                    'toolName' => 'lookup_user',
+                    'toolArgs' => ['userId' => '"101"'],
+                ],
+                'testName' => 'lookup_user',
+            ],
+            'Lookup User Tool (Not Found)' => [
+                'method' => 'tools/call',
+                'options' => [
+                    'toolName' => 'lookup_user',
+                    'toolArgs' => ['userId' => '"999"'],
+                ],
+                'testName' => 'lookup_user_not_found',
+            ],
             'Send Welcome Tool' => [
                 'method' => 'tools/call',
                 'options' => [
diff --git a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user.json b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user.json
new file mode 100644
index 00000000..1399cd26
--- /dev/null
+++ b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user.json
@@ -0,0 +1,16 @@
+{
+  "content": [
+    {
+      "type": "text",
+      "text": "Found user Alice (admin)."
+    },
+    {
+      "name": "user_profile",
+      "uri": "user://101/profile",
+      "description": "Full profile for Alice.",
+      "mimeType": "application/json",
+      "type": "resource_link"
+    }
+  ],
+  "isError": false
+}
diff --git a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user_not_found.json b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user_not_found.json
new file mode 100644
index 00000000..211521cf
--- /dev/null
+++ b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_call-lookup_user_not_found.json
@@ -0,0 +1,9 @@
+{
+  "content": [
+    {
+      "type": "text",
+      "text": "User ID 999 not found."
+    }
+  ],
+  "isError": false
+}
diff --git a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_list.json b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_list.json
index 205ad0ce..08b8198d 100644
--- a/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_list.json
+++ b/tests/Inspector/Http/snapshots/HttpDiscoveryUserProfileTest-tools_list.json
@@ -23,6 +23,22 @@
         ]
       }
     },
+    {
+      "name": "lookup_user",
+      "description": "Looks up a user and returns a reference to their profile resource.\n\nRather than embedding the full profile (as `resources/read` on\n`user://{userId}/profile` would), this returns a `resource_link` block\npointing at that resource template so the caller can fetch it\nseparately if needed. This mirrors how a tool like a search returning\nmany hits would reference each matching resource by URI instead of\ninlining every one of them.",
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "userId": {
+            "type": "string",
+            "description": "the ID of the user to look up"
+          }
+        },
+        "required": [
+          "userId"
+        ]
+      }
+    },
     {
       "name": "send_welcome",
       "description": "Sends a welcome message to a user.\n\n(This is a placeholder - in a real app, it might queue an email).",
diff --git a/tests/Unit/Capability/Formatter/PromptResultFormatterTest.php b/tests/Unit/Capability/Formatter/PromptResultFormatterTest.php
index 53d6dc72..d86d2fe9 100644
--- a/tests/Unit/Capability/Formatter/PromptResultFormatterTest.php
+++ b/tests/Unit/Capability/Formatter/PromptResultFormatterTest.php
@@ -13,6 +13,7 @@
 
 use Mcp\Capability\Formatter\PromptResultFormatter;
 use Mcp\Schema\Content\PromptMessage;
+use Mcp\Schema\Content\ResourceLink;
 use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\Enum\Role;
 use PHPUnit\Framework\TestCase;
@@ -27,6 +28,29 @@ public function testFormatPromptMessage(): void
         $this->assertSame($message, $result[0]);
     }
 
+    public function testFormatPromptMessageWithResourceLinkContent(): void
+    {
+        $message = new PromptMessage(Role::User, new ResourceLink('file:///a.png', 'a.png'));
+        $result = (new PromptResultFormatter())->format($message);
+        $this->assertCount(1, $result);
+        $this->assertSame($message, $result[0]);
+    }
+
+    public function testFormatRoleContentArrayWithResourceLinkContent(): void
+    {
+        $result = (new PromptResultFormatter())->format([
+            [
+                'role' => 'user',
+                'content' => ['type' => 'resource_link', 'uri' => 'file:///a.png', 'name' => 'a.png'],
+            ],
+        ]);
+        $this->assertCount(1, $result);
+        $this->assertSame(Role::User, $result[0]->role);
+        $this->assertInstanceOf(ResourceLink::class, $result[0]->content);
+        $this->assertSame('file:///a.png', $result[0]->content->uri);
+        $this->assertSame('a.png', $result[0]->content->name);
+    }
+
     public function testFormatUserAssistantShorthand(): void
     {
         $result = (new PromptResultFormatter())->format([
diff --git a/tests/Unit/Capability/RegistryTest.php b/tests/Unit/Capability/RegistryTest.php
index c8aa5a7f..3b2d7d7b 100644
--- a/tests/Unit/Capability/RegistryTest.php
+++ b/tests/Unit/Capability/RegistryTest.php
@@ -22,6 +22,8 @@
 use Mcp\Exception\PromptNotFoundException;
 use Mcp\Exception\ResourceNotFoundException;
 use Mcp\Exception\ToolNotFoundException;
+use Mcp\Schema\Content\ResourceLink;
+use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\ResourceDefinition;
 use Mcp\Schema\ResourceTemplate;
@@ -536,6 +538,20 @@ public function testExtractStructuredContentReturnsArrayDirectlyForArrayOutputSc
         ], $structuredContent);
     }
 
+    public function testExtractStructuredContentReturnsNullForArrayOfContentItems(): void
+    {
+        $tool = $this->createValidTool('lookup_thing', null);
+        $toolReturnValue = [
+            new TextContent('Found it.'),
+            new ResourceLink(uri: 'thing://1', name: 'thing_1'),
+        ];
+
+        $this->registry->registerTool($tool, static fn () => $toolReturnValue);
+
+        $toolRef = $this->registry->getTool('lookup_thing');
+        $this->assertNull($toolRef->extractStructuredContent($toolReturnValue));
+    }
+
     public function testConfiguredLoaderIsNotRunUntilFirstRead(): void
     {
         $loader = $this->createMock(LoaderInterface::class);
diff --git a/tests/Unit/Schema/Content/PromptMessageTest.php b/tests/Unit/Schema/Content/PromptMessageTest.php
new file mode 100644
index 00000000..8808d412
--- /dev/null
+++ b/tests/Unit/Schema/Content/PromptMessageTest.php
@@ -0,0 +1,84 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Tests\Unit\Schema\Content;
+
+use Mcp\Exception\InvalidArgumentException;
+use Mcp\Schema\Content\PromptMessage;
+use Mcp\Schema\Content\ResourceLink;
+use Mcp\Schema\Enum\Role;
+use PHPUnit\Framework\TestCase;
+
+final class PromptMessageTest extends TestCase
+{
+    public function testFromArrayDeserializesResourceLinkContent(): void
+    {
+        $message = PromptMessage::fromArray([
+            'role' => 'user',
+            'content' => [
+                'type' => 'resource_link',
+                'uri' => 'file:///project/src/main.rs',
+                'name' => 'main.rs',
+            ],
+        ]);
+
+        $this->assertSame(Role::User, $message->role);
+        $this->assertInstanceOf(ResourceLink::class, $message->content);
+        $this->assertSame('file:///project/src/main.rs', $message->content->uri);
+        $this->assertSame('main.rs', $message->content->name);
+    }
+
+    public function testJsonSerializeIncludesResourceLinkContent(): void
+    {
+        $message = new PromptMessage(Role::Assistant, new ResourceLink('file:///a.png', 'a.png'));
+
+        $this->assertSame([
+            'role' => 'assistant',
+            'content' => [
+                'type' => 'resource_link',
+                'uri' => 'file:///a.png',
+                'name' => 'a.png',
+            ],
+        ], json_decode(json_encode($message), true));
+    }
+
+    public function testRoundTripWithResourceLink(): void
+    {
+        $original = new PromptMessage(Role::User, new ResourceLink('file:///a.png', 'a.png', mimeType: 'image/png'));
+
+        $decoded = json_decode(json_encode($original), true);
+        $rehydrated = PromptMessage::fromArray($decoded);
+
+        $this->assertSame(Role::User, $rehydrated->role);
+        $this->assertInstanceOf(ResourceLink::class, $rehydrated->content);
+        $this->assertSame('file:///a.png', $rehydrated->content->uri);
+        $this->assertSame('image/png', $rehydrated->content->mimeType);
+    }
+
+    public function testFromArrayRejectsUnknownContentType(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        /* @phpstan-ignore argument.type */
+        PromptMessage::fromArray([
+            'role' => 'user',
+            'content' => ['type' => 'not-a-real-type'],
+        ]);
+    }
+
+    public function testConstructorAcceptsResourceLinkContent(): void
+    {
+        $link = new ResourceLink('file:///a.png', 'a.png');
+        $message = new PromptMessage(Role::User, $link);
+
+        $this->assertSame($link, $message->content);
+    }
+}
diff --git a/tests/Unit/Schema/Content/ResourceLinkTest.php b/tests/Unit/Schema/Content/ResourceLinkTest.php
new file mode 100644
index 00000000..3e643774
--- /dev/null
+++ b/tests/Unit/Schema/Content/ResourceLinkTest.php
@@ -0,0 +1,231 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Tests\Unit\Schema\Content;
+
+use Mcp\Exception\InvalidArgumentException;
+use Mcp\Schema\Annotations;
+use Mcp\Schema\Content\ResourceLink;
+use Mcp\Schema\Enum\Role;
+use Mcp\Schema\Icon;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+final class ResourceLinkTest extends TestCase
+{
+    private const VALID_URI = 'file:///project/src/main.rs';
+
+    public function testConstructorSetsType(): void
+    {
+        $link = new ResourceLink(self::VALID_URI, 'main.rs');
+
+        $this->assertSame('resource_link', $link->type);
+        $this->assertSame(self::VALID_URI, $link->uri);
+        $this->assertSame('main.rs', $link->name);
+        $this->assertNull($link->title);
+        $this->assertNull($link->description);
+        $this->assertNull($link->mimeType);
+        $this->assertNull($link->annotations);
+        $this->assertNull($link->size);
+        $this->assertNull($link->icons);
+        $this->assertNull($link->meta);
+    }
+
+    public function testConstructorWithAllFields(): void
+    {
+        $annotations = new Annotations([Role::User], 0.5);
+        $icons = [new Icon('https://example.com/icon.png')];
+
+        $link = new ResourceLink(
+            uri: self::VALID_URI,
+            name: 'main.rs',
+            title: 'Main Source File',
+            description: 'Primary application entry point',
+            mimeType: 'text/x-rust',
+            annotations: $annotations,
+            size: 1024,
+            icons: $icons,
+            meta: ['origin' => 'test'],
+        );
+
+        $this->assertSame(self::VALID_URI, $link->uri);
+        $this->assertSame('main.rs', $link->name);
+        $this->assertSame('Main Source File', $link->title);
+        $this->assertSame('Primary application entry point', $link->description);
+        $this->assertSame('text/x-rust', $link->mimeType);
+        $this->assertSame($annotations, $link->annotations);
+        $this->assertSame(1024, $link->size);
+        $this->assertSame($icons, $link->icons);
+        $this->assertSame(['origin' => 'test'], $link->meta);
+    }
+
+    public function testJsonSerializeMinimal(): void
+    {
+        $link = new ResourceLink(self::VALID_URI, 'main.rs');
+
+        $this->assertSame([
+            'type' => 'resource_link',
+            'uri' => self::VALID_URI,
+            'name' => 'main.rs',
+        ], $link->jsonSerialize());
+    }
+
+    public function testJsonSerializeWithAllFields(): void
+    {
+        $annotations = new Annotations([Role::User], 0.5);
+        $icons = [new Icon('https://example.com/icon.png')];
+
+        $link = new ResourceLink(
+            uri: self::VALID_URI,
+            name: 'main.rs',
+            title: 'Main Source File',
+            description: 'Primary application entry point',
+            mimeType: 'text/x-rust',
+            annotations: $annotations,
+            size: 1024,
+            icons: $icons,
+            meta: ['origin' => 'test'],
+        );
+
+        $data = $link->jsonSerialize();
+
+        $this->assertSame('resource_link', $data['type']);
+        $this->assertSame(self::VALID_URI, $data['uri']);
+        $this->assertSame('main.rs', $data['name']);
+        $this->assertSame('Main Source File', $data['title']);
+        $this->assertSame('Primary application entry point', $data['description']);
+        $this->assertSame('text/x-rust', $data['mimeType']);
+        $this->assertSame($annotations, $data['annotations']);
+        $this->assertSame(1024, $data['size']);
+        $this->assertSame($icons, $data['icons']);
+        $this->assertSame(['origin' => 'test'], $data['_meta']);
+    }
+
+    public function testOptionalFieldsOmittedWhenNull(): void
+    {
+        $link = new ResourceLink(self::VALID_URI, 'main.rs');
+        $data = $link->jsonSerialize();
+
+        $this->assertArrayNotHasKey('title', $data);
+        $this->assertArrayNotHasKey('description', $data);
+        $this->assertArrayNotHasKey('mimeType', $data);
+        $this->assertArrayNotHasKey('annotations', $data);
+        $this->assertArrayNotHasKey('size', $data);
+        $this->assertArrayNotHasKey('icons', $data);
+        $this->assertArrayNotHasKey('_meta', $data);
+    }
+
+    public function testFromArrayMinimal(): void
+    {
+        $link = ResourceLink::fromArray([
+            'type' => 'resource_link',
+            'uri' => self::VALID_URI,
+            'name' => 'main.rs',
+        ]);
+
+        $this->assertSame(self::VALID_URI, $link->uri);
+        $this->assertSame('main.rs', $link->name);
+        $this->assertNull($link->title);
+        $this->assertNull($link->annotations);
+        $this->assertNull($link->icons);
+        $this->assertNull($link->meta);
+    }
+
+    public function testFromArrayWithAllFields(): void
+    {
+        $link = ResourceLink::fromArray([
+            'type' => 'resource_link',
+            'uri' => self::VALID_URI,
+            'name' => 'main.rs',
+            'title' => 'Main Source File',
+            'description' => 'Primary application entry point',
+            'mimeType' => 'text/x-rust',
+            'annotations' => ['audience' => ['user'], 'priority' => 0.5],
+            'size' => 1024,
+            'icons' => [['src' => 'https://example.com/icon.png']],
+            '_meta' => ['origin' => 'test'],
+        ]);
+
+        $this->assertSame('Main Source File', $link->title);
+        $this->assertSame('Primary application entry point', $link->description);
+        $this->assertSame('text/x-rust', $link->mimeType);
+        $this->assertInstanceOf(Annotations::class, $link->annotations);
+        $this->assertSame(1024, $link->size);
+        $this->assertCount(1, $link->icons);
+        $this->assertInstanceOf(Icon::class, $link->icons[0]);
+        $this->assertSame(['origin' => 'test'], $link->meta);
+    }
+
+    public function testRoundTripThroughJsonSerializeAndFromArray(): void
+    {
+        $original = new ResourceLink(
+            uri: self::VALID_URI,
+            name: 'main.rs',
+            title: 'Main Source File',
+            description: 'Primary application entry point',
+            mimeType: 'text/x-rust',
+            annotations: new Annotations([Role::User], 0.5),
+            size: 1024,
+            icons: [new Icon('https://example.com/icon.png')],
+            meta: ['origin' => 'test'],
+        );
+
+        $decoded = json_decode(json_encode($original), true);
+        $rehydrated = ResourceLink::fromArray($decoded);
+
+        $this->assertSame($original->uri, $rehydrated->uri);
+        $this->assertSame($original->name, $rehydrated->name);
+        $this->assertSame($original->title, $rehydrated->title);
+        $this->assertSame($original->description, $rehydrated->description);
+        $this->assertSame($original->mimeType, $rehydrated->mimeType);
+        $this->assertSame($original->size, $rehydrated->size);
+        $this->assertSame($original->meta, $rehydrated->meta);
+        $this->assertEquals($original->annotations, $rehydrated->annotations);
+    }
+
+    public function testFromArrayRejectsWrongType(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Invalid type for ResourceLink.');
+
+        /* @phpstan-ignore argument.type */
+        ResourceLink::fromArray([
+            'type' => 'resource',
+            'uri' => self::VALID_URI,
+            'name' => 'main.rs',
+        ]);
+    }
+
+    #[DataProvider('provideInvalidData')]
+    public function testFromArrayRejectsInvalidData(array $input, string $expectedExceptionMessage): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage($expectedExceptionMessage);
+
+        ResourceLink::fromArray($input);
+    }
+
+    public static function provideInvalidData(): iterable
+    {
+        yield 'missing uri' => [
+            ['type' => 'resource_link', 'name' => 'main.rs'],
+            'Invalid or missing "uri" in ResourceLink data.',
+        ];
+        yield 'missing name' => [
+            ['type' => 'resource_link', 'uri' => self::VALID_URI],
+            'Invalid or missing "name" in ResourceLink data.',
+        ];
+        yield 'invalid _meta' => [
+            ['type' => 'resource_link', 'uri' => self::VALID_URI, 'name' => 'main.rs', '_meta' => 'not-an-array'],
+            'Invalid "_meta" in ResourceLink data.',
+        ];
+    }
+}
diff --git a/tests/Unit/Schema/Result/CallToolResultTest.php b/tests/Unit/Schema/Result/CallToolResultTest.php
new file mode 100644
index 00000000..f7c2b6ff
--- /dev/null
+++ b/tests/Unit/Schema/Result/CallToolResultTest.php
@@ -0,0 +1,112 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Tests\Unit\Schema\Result;
+
+use Mcp\Exception\InvalidArgumentException;
+use Mcp\Schema\Content\AudioContent;
+use Mcp\Schema\Content\EmbeddedResource;
+use Mcp\Schema\Content\ImageContent;
+use Mcp\Schema\Content\ResourceLink;
+use Mcp\Schema\Content\TextContent;
+use Mcp\Schema\Result\CallToolResult;
+use PHPUnit\Framework\TestCase;
+
+final class CallToolResultTest extends TestCase
+{
+    public function testFromArrayDeserializesResourceLinkContent(): void
+    {
+        $result = CallToolResult::fromArray([
+            'content' => [
+                [
+                    'type' => 'resource_link',
+                    'uri' => 'file:///project/src/main.rs',
+                    'name' => 'main.rs',
+                    'mimeType' => 'text/x-rust',
+                ],
+            ],
+            'isError' => false,
+        ]);
+
+        $this->assertCount(1, $result->content);
+        $this->assertInstanceOf(ResourceLink::class, $result->content[0]);
+        $this->assertSame('file:///project/src/main.rs', $result->content[0]->uri);
+        $this->assertSame('main.rs', $result->content[0]->name);
+        $this->assertSame('text/x-rust', $result->content[0]->mimeType);
+    }
+
+    public function testFromArrayDeserializesMixedContentTypes(): void
+    {
+        $result = CallToolResult::fromArray([
+            'content' => [
+                ['type' => 'text', 'text' => 'search results'],
+                ['type' => 'resource_link', 'uri' => 'file:///a.png', 'name' => 'a.png'],
+                ['type' => 'resource_link', 'uri' => 'file:///b.png', 'name' => 'b.png'],
+            ],
+        ]);
+
+        $this->assertCount(3, $result->content);
+        $this->assertInstanceOf(TextContent::class, $result->content[0]);
+        $this->assertInstanceOf(ResourceLink::class, $result->content[1]);
+        $this->assertInstanceOf(ResourceLink::class, $result->content[2]);
+    }
+
+    public function testFromArrayRejectsUnknownContentType(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        CallToolResult::fromArray([
+            'content' => [
+                ['type' => 'not-a-real-type'],
+            ],
+        ]);
+    }
+
+    public function testJsonSerializeIncludesResourceLinkContent(): void
+    {
+        $result = new CallToolResult([
+            new ResourceLink('file:///project/src/main.rs', 'main.rs'),
+        ]);
+
+        $data = $result->jsonSerialize();
+
+        $this->assertSame([
+            'type' => 'resource_link',
+            'uri' => 'file:///project/src/main.rs',
+            'name' => 'main.rs',
+        ], $data['content'][0]->jsonSerialize());
+    }
+
+    public function testRoundTripWithResourceLinkAlongsideOtherContentTypes(): void
+    {
+        $original = new CallToolResult([
+            new TextContent('25 results found'),
+            new ResourceLink('file:///a.png', 'a.png', mimeType: 'image/png'),
+            new ImageContent(base64_encode('binary'), 'image/png'),
+            new AudioContent(base64_encode('binary'), 'audio/mpeg'),
+            EmbeddedResource::fromText('file:///readme.txt', 'hello'),
+        ]);
+
+        $decoded = json_decode(json_encode($original), true);
+        $rehydrated = CallToolResult::fromArray($decoded);
+
+        $this->assertCount(5, $rehydrated->content);
+        $this->assertInstanceOf(TextContent::class, $rehydrated->content[0]);
+        $this->assertInstanceOf(ResourceLink::class, $rehydrated->content[1]);
+        $this->assertInstanceOf(ImageContent::class, $rehydrated->content[2]);
+        $this->assertInstanceOf(AudioContent::class, $rehydrated->content[3]);
+        $this->assertInstanceOf(EmbeddedResource::class, $rehydrated->content[4]);
+
+        $this->assertSame('file:///a.png', $rehydrated->content[1]->uri);
+        $this->assertSame('a.png', $rehydrated->content[1]->name);
+        $this->assertSame('image/png', $rehydrated->content[1]->mimeType);
+    }
+}