feat: add instructions in server initialization result

This update introduces an optional instructions parameter to the Configuration class, allowing for the provision of usage instructions for the server's features, enhancing the InitializeResult with instructions for improved client understanding.

Author: CodeWithKyrian

src/Configuration.php

@@ -26,6 +26,7 @@ class Configuration
      * @param  CacheInterface|null  $cache  Optional PSR-16 Cache instance for registry/state.
      * @param  ContainerInterface  $container  PSR-11 DI Container for resolving handlers/dependencies.
      * @param  int  $paginationLimit  Maximum number of items to return for list methods.
+     * @param  string|null  $instructions  Instructions describing how to use the server and its features.
      */
     public function __construct(
         public readonly Implementation $serverInfo,
@@ -35,5 +36,6 @@ public function __construct(
         public readonly ?CacheInterface $cache,
         public readonly ContainerInterface $container,
         public readonly int $paginationLimit = 50,
+        public readonly ?string $instructions = null,
     ) {}
 }

src/Dispatcher.php

@@ -132,8 +132,9 @@ public function handleInitialize(InitializeRequest $request, SessionInterface $s
 
         $serverInfo = $this->configuration->serverInfo;
         $capabilities = $this->configuration->capabilities;
+        $instructions = $this->configuration->instructions;
 
-        return new InitializeResult($protocolVersion, $capabilities, $serverInfo);
+        return new InitializeResult($protocolVersion, $capabilities, $serverInfo, $instructions);
     }
 
     public function handlePing(PingRequest $request): EmptyResult

src/ServerBuilder.php

@@ -52,6 +52,8 @@ final class ServerBuilder
 
     private ?int $paginationLimit = 50;
 
+    private ?string $instructions = null;
+
     /** @var array<
      *     array{handler: array|string,
      *     name: string|null,
@@ -120,6 +122,20 @@ public function withPaginationLimit(int $paginationLimit): self
         return $this;
     }
 
+    /**
+     * Configures the instructions describing how to use the server and its features. 
+     * 
+     * This can be used by clients to improve the LLM's understanding of available tools, resources,
+     * etc. It can be thought of like a "hint" to the model. For example, this information MAY 
+     * be added to the system prompt.
+     */
+    public function withInstructions(string $instructions): self
+    {
+        $this->instructions = $instructions;
+
+        return $this;
+    }
+
     /**
      * Provides a PSR-3 logger instance. Defaults to NullLogger.
      */
@@ -257,7 +273,8 @@ public function build(): Server
             loop: $loop,
             cache: $cache,
             container: $container,
-            paginationLimit: $this->paginationLimit ?? 50
+            paginationLimit: $this->paginationLimit ?? 50,
+            instructions: $this->instructions,
         );
 
         $sessionHandler = $this->createSessionHandler();