Serialization in ChatClientHelper

[rwhitworth127]

Spent some time troubleshooting an issue today when ChatClient with SemanticKernel. I have several Functions in csharp that return objects instead of strings. When performing a chat completion, Anthropic would run these tools and not actually see the function results.
It appears to be because the ChatClientHelper calls .ToString() when adding ToolResultContent to a message, meaning only the class name and not the json results are being passed to anthropic.

in this section:

case Microsoft.Extensions.AI.FunctionResultContent frc:
    currentMessage.Content.Add(new ToolResultContent()
    {
        ToolUseId = frc.CallId,
        Content = new List<ContentBase>() { new TextContent () { Text = frc.Result?.ToString() ?? string.Empty } },
        IsError = frc.Exception is not null,
    });
    break;

we could consider changing

Text = frc.Result?.ToString() ?? string.Empty

to

Text = frc.Result switch
{
    string s => s,
    null => string.Empty,
    _ => JsonSerializer.Serialize(frc.Result)
}

For now, I have created a workaround in my code by overriding my ToString() method on the result class I have created for each Function.

I haven't tried to test this yet recommendation on the sdk itself, if I get time I could pull it down, test the change, and do a PR. Just posting here in case I am way off base and missing something.