[Examples] Demo pre-built instance handler in combined-registration

Extends the combined-registration example with a third handler style:
a pre-built object instance `[$instance, 'method']`, alongside the
existing discovered and manual class-string handlers. PreconfiguredGreeter
takes a scalar constructor argument neither the container-less
`new $className()` fallback nor the auto-wiring container can build, so it
can only be registered as an already-constructed instance — exercising the
resolver path added in the parent branch.

Adds an inspector snapshot case (tools/call instance_greeter) and updates
the tools/list snapshot.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: chr-hertel

docs/examples.md

@@ -217,14 +217,20 @@ npx @modelcontextprotocol/inspector http://localhost:8000
 **What it demonstrates:**
 - Mixing attribute discovery with manual registration
 - HTTP server with both discovered and manual capabilities
-- Flexible registration patterns
+- All three handler styles: discovered, `[Class::class, 'method']`, and a pre-built `[$instance, 'method']`
+- Pre-built instance handlers for classes the container cannot auto-wire (e.g. constructor scalars)
 
 **Key Features:**
 ```php
+// Built here so its constructor dependencies are injected before registration;
+// the SDK invokes this very instance instead of constructing one itself.
+$preconfiguredGreeter = new PreconfiguredGreeter('Willkommen', logger());
+
 $server = Server::builder()
-    ->setDiscovery(__DIR__, ['.'])  // Automatic discovery
-    ->addTool([ManualHandlers::class, 'manualGreeter'])  // Manual registration
-    ->addResource([ManualHandlers::class, 'getPriorityConfig'], 'config://priority')
+    ->setDiscovery(__DIR__, ['.'])                         // Automatic discovery
+    ->addTool([ManualHandlers::class, 'manualGreeter'])    // Manual class-string handler
+    ->addTool([$preconfiguredGreeter, 'greet'], 'instance_greeter')  // Pre-built instance handler
+    ->addResource([ManualHandlers::class, 'getPriorityConfigManual'], 'config://priority')
 ```
 
 ### Complex Tool Schema

docs/server-builder.md

@@ -277,8 +277,8 @@ Register MCP elements programmatically without using attributes. The handler is
 **Handler** can be any PHP callable:
 
 1. **Closure**: `function(int $a, int $b): int { return $a + $b; }`
-2. **Class and method name pair**: `[ClassName::class, 'methodName']` - class must be constructable through the container
-3. **Class instance and method name**: `[$instance, 'methodName']`
+2. **Class and method name pair**: `[ClassName::class, 'methodName']` - the class is instantiated lazily on first call, so it must be constructable through the container (or have a no-arg constructor)
+3. **Class instance and method name**: `[$instance, 'methodName']` - the given, already-constructed object is invoked as-is. Use this for handlers the container cannot build, e.g. those with scalar constructor arguments or dependencies wired at runtime
 4. **Invokable class name**: `InvokableClass::class` - class must be constructable through the container and have `__invoke` method
 
 ### Manual Tool Registration

examples/server/combined-registration/PreconfiguredGreeter.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.
+ */
+
+namespace Mcp\Example\Server\CombinedRegistration;
+
+use Psr\Log\LoggerInterface;
+
+/**
+ * A handler whose constructor takes a scalar the container cannot auto-wire, so
+ * it can only be registered as a pre-built object instance:
+ * `->addTool([new PreconfiguredGreeter('...', ...), 'greet'], 'instance_greeter')`.
+ *
+ * Neither the container-less `new $className()` fallback nor the auto-wiring
+ * container can build this class, since the required `string $greeting` has no
+ * default and is not a resolvable service.
+ */
+final class PreconfiguredGreeter
+{
+    public function __construct(
+        private readonly string $greeting,
+        private readonly LoggerInterface $logger,
+    ) {
+    }
+
+    /**
+     * A tool registered as a pre-built object instance.
+     *
+     * @param string $name the name to greet
+     *
+     * @return string greeting
+     */
+    public function greet(string $name): string
+    {
+        $this->logger->info("Instance tool 'instance_greeter' called for {$name}");
+
+        return "{$this->greeting}, {$name}!";
+    }
+}

examples/server/combined-registration/server.php

@@ -14,16 +14,23 @@
 chdir(__DIR__);
 
 use Mcp\Example\Server\CombinedRegistration\ManualHandlers;
+use Mcp\Example\Server\CombinedRegistration\PreconfiguredGreeter;
 use Mcp\Server;
 use Mcp\Server\Session\FileSessionStore;
 
+// Built here so its constructor dependencies (a scalar the container cannot
+// auto-wire) are injected before registration; the SDK invokes this very
+// instance instead of trying to construct one itself.
+$preconfiguredGreeter = new PreconfiguredGreeter('Willkommen', logger());
+
 $server = Server::builder()
     ->setServerInfo('Combined HTTP Server', '1.0.0')
     ->setLogger(logger())
     ->setContainer(container())
     ->setSession(new FileSessionStore(__DIR__.'/sessions'))
     ->setDiscovery(__DIR__)
     ->addTool([ManualHandlers::class, 'manualGreeter'])
+    ->addTool([$preconfiguredGreeter, 'greet'], 'instance_greeter')
     ->addResource(
         [ManualHandlers::class, 'getPriorityConfigManual'],
         'config://priority',

tests/Inspector/Http/HttpCombinedRegistrationTest.php

@@ -25,6 +25,14 @@ public static function provideMethods(): array
                 ],
                 'testName' => 'manual_greeter',
             ],
+            'Instance Greeter Tool (pre-built object handler)' => [
+                'method' => 'tools/call',
+                'options' => [
+                    'toolName' => 'instance_greeter',
+                    'toolArgs' => ['name' => 'HTTP Test User'],
+                ],
+                'testName' => 'instance_greeter',
+            ],
             'Discovered Status Check Tool' => [
                 'method' => 'tools/call',
                 'options' => [

tests/Inspector/Http/snapshots/HttpCombinedRegistrationTest-tools_call-instance_greeter.json

@@ -0,0 +1,9 @@
+{
+  "content": [
+    {
+      "type": "text",
+      "text": "Willkommen, HTTP Test User!"
+    }
+  ],
+  "isError": false
+}

tests/Inspector/Http/snapshots/HttpCombinedRegistrationTest-tools_list.json

@@ -16,6 +16,22 @@
         ]
       }
     },
+    {
+      "name": "instance_greeter",
+      "description": "A tool registered as a pre-built object instance.",
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "name": {
+            "type": "string",
+            "description": "the name to greet"
+          }
+        },
+        "required": [
+          "name"
+        ]
+      }
+    },
     {
       "name": "discovered_status_check",
       "description": "A tool discovered via attributes.",