Add doc explaination

Author: camilleislasse

docs/bundles/mcp-bundle.rst

@@ -29,6 +29,44 @@ Creating MCP Capabilities
 
 MCP capabilities are automatically discovered using PHP attributes.
 
+.. warning::
+
+    The MCP Bundle currently **only supports the invokable pattern** where attributes are placed on classes
+    with an ``__invoke()`` method. The method pattern (attributes on individual methods) is **not supported**.
+
+    This is because Symfony's ``registerAttributeForAutoconfiguration()`` only detects class-level attributes,
+    not method-level attributes. While the underlying MCP SDK supports both patterns, the Bundle's
+    autoconfiguration mechanism requires the invokable pattern.
+
+    **Supported pattern** (invokable)::
+
+        #[McpTool(name: 'my-tool')]
+        class MyTool
+        {
+            public function __invoke(string $param): string
+            {
+                // Implementation
+            }
+        }
+
+    **Not supported pattern** (method-based)::
+
+        class MyTools
+        {
+            #[McpTool(name: 'tool-one')]  // Discovered but no DI support
+            public function toolOne(): string { }
+
+            #[McpTool(name: 'tool-two')]  // Discovered but no DI support
+            public function toolTwo(): string { }
+        }
+
+    Method-based attributes are discovered by the MCP SDK, but the class is not registered as a
+    Symfony service. This means **constructor dependencies will not be injected** and the tool will
+    fail if it requires any services.
+
+    This limitation applies to all MCP capability attributes: ``#[McpTool]``, ``#[McpPrompt]``,
+    ``#[McpResource]``, and ``#[McpResourceTemplate]``.
+
 Tools
 ^^^^^