#21 Add support for MCP resources in server capabilities

Implemented the `supportsResources` feature in `ServerCapabilities` to enable resource registration and exposure to clients. Updated related methods, serialization logic, and tests to account for resources configuration. Extended `MCPServer` to integrate resources functionality seamlessly.

Author: klapaudius

src/Server/MCPServer.php

@@ -122,7 +122,7 @@ public function registerToolRepository(ToolRepository $toolRepository): self
     {
         $this->registerRequestHandler(new ToolsListHandler($toolRepository));
         $this->registerRequestHandler(new ToolsCallHandler($toolRepository));
-        $this->capabilities = (new ServerCapabilities)->withTools($toolRepository->getToolSchemas());
+        $this->capabilities->withTools($toolRepository->getToolSchemas());
 
         return $this;
     }
@@ -131,6 +131,7 @@ public function registerResourceRepository(ResourceRepository $resourceRepositor
     {
         $this->registerRequestHandler(new ResourcesListHandler($resourceRepository));
         $this->registerRequestHandler(new ResourcesReadHandler($resourceRepository));
+        $this->capabilities->withResources($resourceRepository->getResourceSchemas());
 
         return $this;
     }

src/Server/ServerCapabilities.php

@@ -20,6 +20,14 @@ final class ServerCapabilities implements ServerCapabilitiesInterface
      */
     private bool $supportsTools = false;
 
+    /**
+     * Indicates whether the server supports the MCP resources feature.
+     * If true, the server can register and expose resources to the client.
+     *
+     * @see https://modelcontextprotocol.io/docs/concepts/resources
+     */
+    private bool $supportsResources = false;
+
     /**
      * Optional configuration specific to the tools capability.
      * This structure can be defined by the specific server implementation
@@ -28,6 +36,12 @@ final class ServerCapabilities implements ServerCapabilitiesInterface
      */
     private ?array $toolsConfig = null;
 
+    /**
+     * Optional configuration specific to the resources capability.
+     * This structure can be defined by the specific server implementation
+     */
+    private ?array $resourcesConfig = null;
+
     /**
      * Enables the tools capability for the server instance.
      * Allows specifying optional configuration details for the tools feature.
@@ -46,6 +60,24 @@ public function withTools(?array $config = []): self
         return $this;
     }
 
+    /**
+     * Enables the tools capability for the server instance.
+     * Allows specifying optional configuration details for the tools feature.
+     *
+     * @param  array|null  $config  Optional configuration data specific to the tools capability.
+     *                              Defaults to an empty array if not provided.
+     * @return self Returns the instance for method chaining.
+     *
+     * @see https://modelcontextprotocol.io/docs/concepts/tools
+     */
+    public function withResources(?array $config = []): self
+    {
+        $this->supportsResources = true;
+        $this->resourcesConfig = $config;
+
+        return $this;
+    }
+
     /**
      * Converts the server capabilities configuration into an array format suitable for JSON serialization.
      * Only includes capabilities that are actively enabled.
@@ -57,7 +89,7 @@ public function toArray(): array
     {
         $capabilities = [
             'prompts' => new stdClass,
-            'resources' => new stdClass,
+            'resources' => $this->supportsResources ? $this->resourcesConfig : new stdClass,
         ];
 
         if ($this->supportsTools) {
@@ -83,6 +115,9 @@ public function toInitializeMessage(): array
         if ($this->supportsTools) {
             $capabilities['tools']->listChanged = true;
         }
+        if ($this->supportsResources) {
+            $capabilities['resources']->listChanged = true;
+        }
 
         return $capabilities;
     }

tests/Server/MCPServerTest.php

@@ -12,6 +12,7 @@
 use KLP\KlpMcpServer\Server\MCPServer;
 use KLP\KlpMcpServer\Server\Request\ToolsCallHandler;
 use KLP\KlpMcpServer\Server\Request\ToolsListHandler;
+use KLP\KlpMcpServer\Server\ServerCapabilities;
 use KLP\KlpMcpServer\Server\ServerCapabilitiesInterface;
 use KLP\KlpMcpServer\Services\ToolService\ToolRepository;
 use PHPUnit\Framework\Attributes\Small;
@@ -41,6 +42,7 @@ public function test_register_tool_repository(): void
 
         $server = new ReflectionClass(MCPServer::class);
         $instance = $server->newInstanceWithoutConstructor();
+        $server->getProperty('capabilities')->setValue($instance, new ServerCapabilities);
         $server->getProperty('protocol')->setValue($instance, $mockProtocol);
 
         // Act
@@ -57,6 +59,7 @@ public function test_register_tool_repository_returns_instance(): void
 
         $server = new ReflectionClass(MCPServer::class);
         $instance = $server->newInstanceWithoutConstructor();
+        $server->getProperty('capabilities')->setValue($instance, new ServerCapabilities);
         $server->getProperty('protocol')->setValue($instance, $mockProtocol);
 
         // Act