File Server/Handler/Request/CallToolRequestHandler.php

1:	<?php
2:
3:	declare(strict_types=1);
4:
5:	/**
6:	* This file is part of the Nexus MCP SDK package.
7:	*
8:	* (c) 2026 John Paul E. Balandan, CPA <paulbalandan@gmail.com>
9:	*
10:	* For the full copyright and license information, please view
11:	* the LICENSE file that was distributed with this source code.
12:	*/
13:
14:	namespace Nexus\Mcp\Server\Handler\Request;
15:
16:	use Nexus\Mcp\Core\Exception\AbstractJsonRpcProtocolException;
17:	use Nexus\Mcp\Core\Handler\AbstractContext;
18:	use Nexus\Mcp\Core\Handler\RequestHandlerInterface;
19:	use Nexus\Mcp\Core\Schema\ContentBlock\TextContent;
20:	use Nexus\Mcp\Core\Schema\JsonRpc\JsonRpcRequest;
21:	use Nexus\Mcp\Core\Schema\Request\CallToolRequest;
22:	use Nexus\Mcp\Core\Schema\Result\CallToolResult;
23:	use Nexus\Mcp\Core\Schema\Result\InputRequiredResult;
24:	use Nexus\Mcp\Server\Exception\ToolOutputValidationException;
25:	use Nexus\Mcp\Server\ServerContext;
26:	use Nexus\Mcp\Server\Tool\ToolStoreInterface;
27:	use Psr\Log\LoggerInterface;
28:	use Psr\Log\NullLogger;
29:
30:	/**
31:	* Handles the `tools/call` request by delegating to a `ToolStoreInterface`.
32:	*
33:	* @implements RequestHandlerInterface<'tools/call', CallToolResult\|InputRequiredResult, ServerContext>
34:	*/
35:	final readonly class CallToolRequestHandler implements RequestHandlerInterface
36:	{
37:	public function __construct(private ToolStoreInterface $store, private LoggerInterface $logger = new NullLogger())
38:	{
39:	}
40:
41:	#[\Override]
42:	public function handle(JsonRpcRequest $request, AbstractContext $context): CallToolResult\|InputRequiredResult
43:	{
44:	\assert($request instanceof CallToolRequest);
45:	\assert($context instanceof ServerContext);
46:
47:	try {
48:	$result = $this->store->call($request->params->name, $request->params->arguments, $context);
49:
50:	if ($result instanceof InputRequiredResult) {
51:	// The tool is asking the client for input, so it has produced no content to back-fill.
52:	return $result;
53:	}
54:
55:	// Spec, "Structured Content": "For backwards compatibility, a tool that returns
56:	// structured content SHOULD also return the serialized JSON in a TextContent block."
57:	if (null !== $result->structuredContent && [] === $result->content) {
58:	return new CallToolResult(
59:	content: [new TextContent(text: json_encode(
60:	$result->structuredContent,
61:	\JSON_THROW_ON_ERROR \| \JSON_UNESCAPED_SLASHES \| \JSON_UNESCAPED_UNICODE,
62:	))],
63:	structuredContent: $result->structuredContent,
64:	isError: $result->isError,
65:	meta: $result->meta,
66:	);
67:	}
68:
69:	return $result;
70:	} catch (AbstractJsonRpcProtocolException $e) {
71:	throw $e;
72:	} catch (ToolOutputValidationException $e) {
73:	$this->logger->error(
74:	'Tool returned structuredContent that does not conform to its outputSchema.',
75:	['tool' => $request->params->name, 'exception' => $e],
76:	);
77:
78:	return new CallToolResult(
79:	content: [new TextContent(text: 'Tool execution failed.')],
80:	isError: true,
81:	);
82:	} catch (\Throwable $e) {
83:	// Generic peer-facing text. Raw $e->getMessage() can carry paths or secrets.
84:	$this->logger->error(
85:	'Uncaught tool executor exception. Returning generic error to peer.',
86:	['tool' => $request->params->name, 'exception' => $e],
87:	);
88:
89:	return new CallToolResult(
90:	content: [new TextContent(text: 'Tool execution failed.')],
91:	isError: true,
92:	);
93:	}
94:	}
95:	}
96:

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