Wire up notifications for changing prompt, resource & tools lists

Author: chr-hertel

composer.json

@@ -54,6 +54,7 @@
   "autoload-dev": {
     "psr-4": {
       "Mcp\\Example\\Server\\CachedDiscovery\\": "examples/server/cached-discovery/",
+      "Mcp\\Example\\Server\\ChangeEvents\\": "examples/server/change-events/",
       "Mcp\\Example\\Server\\ClientCommunication\\": "examples/server/client-communication/",
       "Mcp\\Example\\Server\\ClientLogging\\": "examples/server/client-logging/",
       "Mcp\\Example\\Server\\CombinedRegistration\\": "examples/server/combined-registration/",

examples/server/change-events/ListChangingHandlers.php

@@ -0,0 +1,66 @@
+<?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\Example\Server\ChangeEvents;
+
+use Mcp\Capability\RegistryInterface;
+use Mcp\Schema\Content\PromptMessage;
+use Mcp\Schema\Content\TextContent;
+use Mcp\Schema\Enum\Role;
+use Mcp\Schema\Prompt;
+use Mcp\Schema\Resource;
+use Mcp\Schema\Tool;
+
+final class ListChangingHandlers
+{
+    public function __construct(
+        private readonly RegistryInterface $registry,
+    ) {
+    }
+
+    public function addPrompt(string $name, string $content): string
+    {
+        $this->registry->registerPrompt(
+            new Prompt($name),
+            static fn () => [new PromptMessage(Role::User, new TextContent($content))],
+            isManual: true,
+        );
+
+        return \sprintf('Prompt "%s" registered.', $name);
+    }
+
+    public function addResource(string $uri, string $name): string
+    {
+        $this->registry->registerResource(
+            new Resource($uri, $name),
+            static fn () => \sprintf('This is the content of the dynamically added resource "%s" at URI "%s".', $name, $uri),
+            true,
+        );
+
+        return \sprintf('Resource "%s" registered.', $name);
+    }
+
+    public function addTool(string $name): string
+    {
+        $this->registry->registerTool(
+            new Tool(
+                $name,
+                ['type' => 'object', 'properties' => new \stdClass(), 'required' => []],
+                'Dynamically added tool',
+                null
+            ),
+            static fn () => \sprintf('This is the output of the dynamically added tool "%s".', $name),
+            true,
+        );
+
+        return \sprintf('Tool "%s" registered.', $name);
+    }
+}

examples/server/change-events/server.php

@@ -0,0 +1,46 @@
+<?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.
+ */
+
+require_once dirname(__DIR__).'/bootstrap.php';
+chdir(__DIR__);
+
+use Mcp\Capability\Registry;
+use Mcp\Capability\RegistryInterface;
+use Mcp\Event\Dispatcher;
+use Mcp\Event\ListenerProvider;
+use Mcp\Example\Server\ChangeEvents\ListChangingHandlers;
+use Mcp\Server;
+
+logger()->info('Starting MCP Change Events Server...');
+
+$listenerProvider = new ListenerProvider();
+$dispatcher = new Dispatcher($listenerProvider);
+$registry = new Registry($dispatcher, logger());
+$container = container();
+$container->set(RegistryInterface::class, $registry);
+
+$server = Server::builder()
+    ->setServerInfo('Server with Changing Lists', '1.0.0')
+    ->setLogger(logger())
+    ->setContainer($container)
+    ->setRegistry($registry)
+    ->setEventDispatcher($dispatcher)
+    ->setEventListenerProvider($listenerProvider)
+    ->addTool([ListChangingHandlers::class, 'addPrompt'], 'add_prompt', 'Tool that adds a new prompt to the registry with the given name and content.')
+    ->addTool([ListChangingHandlers::class, 'addResource'], 'add_resource', 'Tool that adds a new resource to the registry with the given name and URL.')
+    ->addTool([ListChangingHandlers::class, 'addTool'], 'add_tool', 'Tool that adds a new tool to the registry with the given name.')
+    ->build();
+
+$result = $server->run(transport());
+
+logger()->info('Server listener stopped gracefully.', ['result' => $result]);
+
+shutdown($result);

src/Event/Dispatcher.php

@@ -0,0 +1,34 @@
+<?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\Event;
+
+use Psr\EventDispatcher\EventDispatcherInterface;
+
+/**
+ * @author Christopher Hertel <mail@christopher-hertel.de>
+ */
+final class Dispatcher implements EventDispatcherInterface
+{
+    public function __construct(
+        private readonly ListenerProvider $listenerProvider,
+    ) {
+    }
+
+    public function dispatch(object $event): object
+    {
+        foreach ($this->listenerProvider->getListenersForEvent($event) as $listener) {
+            $listener($event);
+        }
+
+        return $event;
+    }
+}

src/Event/ListenerProvider.php

@@ -0,0 +1,44 @@
+<?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\Event;
+
+use Psr\EventDispatcher\ListenerProviderInterface;
+
+/**
+ * Intended for SDK internal event listeners.
+ *
+ * @author Christopher Hertel <mail@christopher-hertel.de>
+ */
+final class ListenerProvider implements ListenerProviderInterface
+{
+    /**
+     * @var array <class-string, callable[]>
+     */
+    private array $listeners = [];
+
+    public function addListener(string $eventClass, callable $listener): void
+    {
+        $this->listeners[$eventClass][] = $listener;
+    }
+
+    /**
+     * @return iterable<callable>
+     */
+    public function getListenersForEvent(object $event): iterable
+    {
+        if (isset($this->listeners[$event::class])) {
+            foreach ($this->listeners[$event::class] as $listener) {
+                yield $listener;
+            }
+        }
+    }
+}

src/Schema/Tool.php

@@ -21,8 +21,8 @@
  *
  * @phpstan-type ToolInputSchema array{
  *     type: 'object',
- *     properties: array<string, mixed>,
- *     required: string[]|null
+ *     properties: array<string, mixed>|object,
+ *     required: string[]
  * }
  * @phpstan-type ToolOutputSchema array{
  *     type: 'object',

src/Server/Builder.php

@@ -23,6 +23,11 @@
 use Mcp\Capability\Registry\Loader\LoaderInterface;
 use Mcp\Capability\Registry\ReferenceHandler;
 use Mcp\Capability\RegistryInterface;
+use Mcp\Event\Dispatcher;
+use Mcp\Event\ListenerProvider;
+use Mcp\Event\PromptListChangedEvent;
+use Mcp\Event\ResourceListChangedEvent;
+use Mcp\Event\ToolListChangedEvent;
 use Mcp\JsonRpc\MessageFactory;
 use Mcp\Schema\Annotations;
 use Mcp\Schema\Enum\ProtocolVersion;
@@ -60,6 +65,8 @@ final class Builder
 
     private ?EventDispatcherInterface $eventDispatcher = null;
 
+    private ?ListenerProvider $eventListenerProvider = null;
+
     private ?ContainerInterface $container = null;
 
     private ?SchemaGeneratorInterface $schemaGenerator = null;
@@ -284,6 +291,13 @@ public function setEventDispatcher(EventDispatcherInterface $eventDispatcher): s
         return $this;
     }
 
+    public function setEventListenerProvider(ListenerProvider $listenerProvider): self
+    {
+        $this->eventListenerProvider = $listenerProvider;
+
+        return $this;
+    }
+
     /**
      * Provides a PSR-11 DI container, primarily for resolving user-defined handler classes.
      * Defaults to a basic internal container.
@@ -488,6 +502,8 @@ public function build(): Server
     {
         $logger = $this->logger ?? new NullLogger();
         $container = $this->container ?? new Container();
+        $this->eventListenerProvider ??= new ListenerProvider();
+        $this->eventDispatcher ??= new Dispatcher($this->eventListenerProvider);
         $registry = $this->registry ?? new Registry($this->eventDispatcher, $logger);
 
         $loaders = [
@@ -511,12 +527,12 @@ public function build(): Server
 
         $capabilities = $this->serverCapabilities ?? new ServerCapabilities(
             tools: $registry->hasTools(),
-            toolsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            toolsListChanged: true,
             resources: $registry->hasResources() || $registry->hasResourceTemplates(),
             resourcesSubscribe: false,
-            resourcesListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            resourcesListChanged: true,
             prompts: $registry->hasPrompts(),
-            promptsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            promptsListChanged: true,
             logging: true,
             completions: true,
         );
@@ -552,6 +568,11 @@ public function build(): Server
             logger: $logger,
         );
 
+        $changeListener = new ChangeListener($protocol);
+        $this->eventListenerProvider->addListener(PromptListChangedEvent::class, $changeListener->onPromptListChange(...));
+        $this->eventListenerProvider->addListener(ResourceListChangedEvent::class, $changeListener->onResourceListChange(...));
+        $this->eventListenerProvider->addListener(ToolListChangedEvent::class, $changeListener->onToolListChange(...));
+
         return new Server($protocol, $logger);
     }
 

src/Server/ChangeListener.php

@@ -0,0 +1,42 @@
+<?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\Server;
+
+use Mcp\Schema\Notification\PromptListChangedNotification;
+use Mcp\Schema\Notification\ResourceListChangedNotification;
+use Mcp\Schema\Notification\ToolListChangedNotification;
+
+/**
+ * @author Christopher Hertel <mail@christopher-hertel.de>
+ */
+final class ChangeListener
+{
+    public function __construct(
+        private readonly Protocol $protocol,
+    ) {
+    }
+
+    public function onPromptListChange(): void
+    {
+        $this->protocol->sendNotification(new PromptListChangedNotification());
+    }
+
+    public function onResourceListChange(): void
+    {
+        $this->protocol->sendNotification(new ResourceListChangedNotification());
+    }
+
+    public function onToolListChange(): void
+    {
+        $this->protocol->sendNotification(new ToolListChangedNotification());
+    }
+}