diff --git a/composer.json b/composer.json
index 5d1c5297..46ea2d77 100644
--- a/composer.json
+++ b/composer.json
@@ -32,9 +32,11 @@
     "psr/http-server-handler": "^1.0",
     "psr/http-server-middleware": "^1.0",
     "psr/log": "^1.0 || ^2.0 || ^3.0",
-    "symfony/finder": "^5.4 || ^6.4 || ^7.3 || ^8.0",
     "symfony/uid": "^5.4 || ^6.4 || ^7.3 || ^8.0"
   },
+  "suggest": {
+    "symfony/finder": "Required for file-based discovery."
+  },
   "require-dev": {
     "ext-openssl": "*",
     "composer/semver": "^3.0",
@@ -50,6 +52,7 @@
     "psr/simple-cache": "^2.0 || ^3.0",
     "symfony/cache": "^5.4 || ^6.4 || ^7.3 || ^8.0",
     "symfony/console": "^5.4 || ^6.4 || ^7.3 || ^8.0",
+    "symfony/finder": "^5.4 || ^6.4 || ^7.3 || ^8.0",
     "symfony/http-client": "^5.4 || ^6.4 || ^7.3 || ^8.0",
     "symfony/process": "^5.4 || ^6.4 || ^7.3 || ^8.0"
   },
diff --git a/src/Capability/Discovery/Discoverer.php b/src/Capability/Discovery/Discoverer.php
index 3b9ed3a9..c682027a 100644
--- a/src/Capability/Discovery/Discoverer.php
+++ b/src/Capability/Discovery/Discoverer.php
@@ -24,6 +24,7 @@
 use Mcp\Capability\Registry\ResourceTemplateReference;
 use Mcp\Capability\Registry\ToolReference;
 use Mcp\Exception\ExceptionInterface;
+use Mcp\Exception\RuntimeException;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\PromptArgument;
 use Mcp\Schema\Resource;
@@ -53,6 +54,10 @@ public function __construct(
         private ?DocBlockParser $docBlockParser = null,
         private ?SchemaGeneratorInterface $schemaGenerator = null,
     ) {
+        if (!class_exists(Finder::class)) {
+            throw new RuntimeException('File-based discovery requires symfony/finder. Run: composer require symfony/finder');
+        }
+
         $this->docBlockParser = $docBlockParser ?? new DocBlockParser(logger: $this->logger);
         $this->schemaGenerator = $schemaGenerator ?? new SchemaGenerator($this->docBlockParser);
     }