.Net: Bug: Unsupported content type. FunctionCallContent is not supported by Gemini.

[donatas-xyz]

Describe the bug
Unsupported content type. FunctionCallContent is not supported by Gemini. error when calling plugin functions after upgrading from Microsoft.SemanticKernel.Connectors.Google 1.47.0-alpha to 1.48.0-alpha.

To Reproduce

[KernelFunction]
[Description("Returns the current date.")]
public async Task<string> CurrentDate()
{
    return await Task.FromResult(DateTime.Now.ToLongDateString());
}

Gemini, what's today's date?

Expected behavior
After reverting back to 1.47.0-alpha

Today is 30 April 2025.

Platform

• Language: C#, .NET 9
• Source:Microsoft.SemanticKernel.Connectors.Google 1.48.0-alpha
• AI model: gemini-2.0-flash
• IDE: Visual Studio
• OS: Windows 11
• Semantic Kernel: 1.48.0

Additional context
Just quickly reporting. I haven't checked for breaking changes or done any other investigation other than a quick Google search.