Laravel MCP tool responses causes validation error due to Response::structured() returning a ResponseFactory instead of Response

[schaeferalex]

When defining a Laravel MCP tool using the laravel/mcp package, tool calls that return structured responses fail validation in Prism.

public function handle(Request $request): Response
{
    $user = new User;
    $user->firstname = $request->get('firstname');
    $user->lastname = $request->get('lastname');
    $user->save();

    return Response::structured([
        'id' => $user->id,
    ]);
}

public function schema(JsonSchema $schema): array
{
    return [
        'firstname' => $schema->string()
            ->description('The firstname of the user.'),

        'lastname' => $schema->string()
            ->description('The lastname of the user.'),
    ];
}

Prism throws the following error when the tool is invoked:

Parameter validation error: Type mismatch. Expected: [firstname (RawSchema), lastname (RawSchema). 
Received: {"firstname":"John","lastname":"Doe"}. Please provide correct parameter types and names.

It appears that Response::structured() returns a ResponseFactory, not a Response. Prism’s LaravelMcpTool adapter, however, expects a Response. As a result, the adapter fails to process the output correctly, leading Prism to misinterpret the input parameters and throw a type-mismatch validation error.

As a temporary fix, if you change the return value to Response::json(), the tool call will work as expected.