feat: include tool definitions to system prompt

src/Chain/InputProcessor/SystemPromptInputProcessor.php

@@ -6,14 +6,21 @@
 
 use PhpLlm\LlmChain\Chain\Input;
 use PhpLlm\LlmChain\Chain\InputProcessor;
+use PhpLlm\LlmChain\Chain\ToolBox\Metadata;
+use PhpLlm\LlmChain\Chain\ToolBox\ToolBoxInterface;
 use PhpLlm\LlmChain\Model\Message\Message;
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 
 final readonly class SystemPromptInputProcessor implements InputProcessor
 {
+    /**
+     * @param string                $systemPrompt the system prompt to prepend to the input messages
+     * @param ToolBoxInterface|null $toolBox      the tool box to be used to append the tool definitions to the system prompt
+     */
     public function __construct(
         private string $systemPrompt,
+        private ?ToolBoxInterface $toolBox = null,
         private LoggerInterface $logger = new NullLogger(),
     ) {
     }
@@ -28,6 +35,30 @@ public function processInput(Input $input): void
             return;
         }
 
-        $input->messages = $messages->prepend(Message::forSystem($this->systemPrompt));
+        $message = $this->systemPrompt;
+
+        if ($this->toolBox instanceof ToolBoxInterface
+            && [] !== $this->toolBox->getMap()
+        ) {
+            $this->logger->debug('Append tool definitions to system prompt.');
+
+            $tools = implode(PHP_EOL.PHP_EOL, array_map(
+                fn (Metadata $tool) => <<<TOOL
+                    ## {$tool->name}
+                    {$tool->description}
+                    TOOL,
+                $this->toolBox->getMap()
+            ));
+
+            $message = <<<PROMPT
+                {$this->systemPrompt}
+
+                # Available tools
+
+                {$tools}
+                PROMPT;
+        }
+
+        $input->messages = $messages->prepend(Message::forSystem($message));
     }
 }

tests/Chain/InputProcessor/SystemPromptInputProcessorTest.php

@@ -7,11 +7,16 @@
 use PhpLlm\LlmChain\Bridge\OpenAI\GPT;
 use PhpLlm\LlmChain\Chain\Input;
 use PhpLlm\LlmChain\Chain\InputProcessor\SystemPromptInputProcessor;
+use PhpLlm\LlmChain\Chain\ToolBox\Metadata;
+use PhpLlm\LlmChain\Chain\ToolBox\ToolBoxInterface;
 use PhpLlm\LlmChain\Model\Message\Content\Text;
 use PhpLlm\LlmChain\Model\Message\Message;
 use PhpLlm\LlmChain\Model\Message\MessageBag;
 use PhpLlm\LlmChain\Model\Message\SystemMessage;
 use PhpLlm\LlmChain\Model\Message\UserMessage;
+use PhpLlm\LlmChain\Model\Response\ToolCall;
+use PhpLlm\LlmChain\Tests\Fixture\Tool\ToolNoParams;
+use PhpLlm\LlmChain\Tests\Fixture\Tool\ToolRequiredParams;
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Small;
 use PHPUnit\Framework\Attributes\Test;
@@ -62,4 +67,83 @@ public function processInputDoesNotAddSystemMessageWhenOneExists(): void
         self::assertInstanceOf(UserMessage::class, $messages[1]);
         self::assertSame('This is already a system prompt', $messages[0]->content);
     }
+
+    #[Test]
+    public function doesNotIncludeToolsIfToolboxIsEmpty(): void
+    {
+        $processor = new SystemPromptInputProcessor(
+            'This is a system prompt',
+            new class implements ToolBoxInterface {
+                public function getMap(): array
+                {
+                    return [];
+                }
+
+                public function execute(ToolCall $toolCall): mixed
+                {
+                    return null;
+                }
+            }
+        );
+
+        $input = new Input(new GPT(), new MessageBag(Message::ofUser('This is a user message')), []);
+        $processor->processInput($input);
+
+        $messages = $input->messages->getMessages();
+        self::assertCount(2, $messages);
+        self::assertInstanceOf(SystemMessage::class, $messages[0]);
+        self::assertInstanceOf(UserMessage::class, $messages[1]);
+        self::assertSame('This is a system prompt', $messages[0]->content);
+    }
+
+    #[Test]
+    public function includeToolDefinitions(): void
+    {
+        $processor = new SystemPromptInputProcessor(
+            'This is a system prompt',
+            new class implements ToolBoxInterface {
+                public function getMap(): array
+                {
+                    return [
+                        new Metadata(ToolNoParams::class, 'tool_no_params', 'A tool without parameters', '__invoke', null),
+                        new Metadata(
+                            ToolRequiredParams::class,
+                            'tool_required_params',
+                            <<<DESCRIPTION
+                                A tool with required parameters
+                                or not
+                                DESCRIPTION,
+                            'bar',
+                            null
+                        ),
+                    ];
+                }
+
+                public function execute(ToolCall $toolCall): mixed
+                {
+                    return null;
+                }
+            }
+        );
+
+        $input = new Input(new GPT(), new MessageBag(Message::ofUser('This is a user message')), []);
+        $processor->processInput($input);
+
+        $messages = $input->messages->getMessages();
+        self::assertCount(2, $messages);
+        self::assertInstanceOf(SystemMessage::class, $messages[0]);
+        self::assertInstanceOf(UserMessage::class, $messages[1]);
+        self::assertSame(<<<PROMPT
+            This is a system prompt
+
+            # Available tools
+
+            ## tool_no_params
+            A tool without parameters
+
+            ## tool_required_params
+            A tool with required parameters
+            or not
+            PROMPT, $messages[0]->content);
+    }
 }