[Platform] Using MCP Remote servers as Tools

[lochmueller]

Hey everyone,

currently, it is not possible to use remote MCP servers in as Tools for requests to the models.
It is possible to run this requests against the responses API: https://cookbook.openai.com/examples/mcp/mcp_tool_guide
As result the Model will directly call the MCP server and do not get in a "ping pong" conversation with symfony/aiI.

Example:

        $data = [
            "model" => 'gpt-4',
            "input" => 'Wann kommt der Restmüll an dieser Adresse: Schürhornweg 1, 33649 Bielefeld, DE?',
            "tools" => [
                [
                    "type" => "mcp",
                    "server_label" => "dmcp",
                    "server_description" => "Get the garbage information for addresses in germany.",
                    "server_url" => "https://xn--mll-hoa.io/mcp", // This is müll.io
                    "require_approval" => "never",
                    "allowed_tools" => ["fetch-garbage-information-via-address"],
                ]
            ],
        ];

        $this->httpClient->request('POST', \sprintf('%s/v1/responses', '.........'), [
            'json' => $data,
            'headers' => [
                'Authorization' => 'Bearer .........',
                'Content-Type' => 'application/json',
            ],
        ]);

       // Output is: "Der nächste Abholtermin für den Restmüll an der Adresse Schürhornweg 1, 33649 Bielefeld, DE ist am 30.09.2025."

I think about an integration, but have no idea how to start in the right way. Any ideas? Currently, there is the AsTool attribute, but an Attribute is only useful, if there is an integration. So the remote MCP is just configuration? Or a new Attribute like AsMcpRemoteServerTool incl. the needed parameters. Furthermore, I have to integrate the /responses-endpoint in separated client for a Bridge?!? Should I keep platform->invoke with a new Input object instead of Messages?

Any ideas are welcome :)

Regards,
Tim

[chr-hertel]

Wait, I'm confused, you would want to call the OpenAI API, provide the tool, but use that via MCP?
Why?

So, I do get that we should be able

• to easily expose tools when acting as MCP Server -> that's rather MCP SDK + Bundle
• to enable the Agent to act as MCP client to use MCP Servers -> Agent Component Toolbox

Can you describe more what your app is meant to provide?

[lochmueller]

Hey @chr-hertel,

maybe I’m looking in the wrong places. My goal is to use the model to directly call a set of different MCP servers out there (with or without authentication—the example above is an open MCP endpoint). The example above is a working case: GPT-4 calls the MCP server directly, retrieves the information, and uses it (e.g., rendering it in the output).

Currently—as far as I can see—it’s only possible to define tools that are passed through the toolbox. However, tools are always an interaction between the model and Symfony/AI. That means when the model wants to use a tool, it selects it in the response, and Symfony/AI sends the answer in a separate request. MCP, on the other hand, can be made directly “known” to the model.

This means that, on the one hand, the endpoint needs to be replaced (including response parsing), and on the other hand, it should also be possible to support “other tools” that are not of type function.

Or am I missing something?

Regards,
Tim

[chr-hertel]

Okay gotcha, thanks, yeah we shouldn't us AsTool for that - and we don't need the Agent/Toolbox here.

I think it should rather be similar to what we have with Gemini/Vertex Server Tools. Like an option, that is passend via invoke and gets merged into the tools payload in OpenAI ModelClient

[chr-hertel]

I wonder if it's sufficient to create a VO for

"server_label" => "dmcp",
"server_description" => "Get the garbage information for addresses in germany.",
"server_url" => "https://xn--mll-hoa.io/mcp", // This is müll.io
"require_approval" => "never",
"allowed_tools" => ["fetch-garbage-information-via-address"],

That is handed over:

$platform->invoke($model, $input, [
    'server_tools' => new Mcp(...),
]);