How in error handling action determine should I return web view or api response

In Asp.net Core project I have both web UI and Web API controllers. I followed https://www.devtrends.co.uk/blog/handling-errors-in-asp.net-core-web-api article and included in startup.cs:

app.UseStatusCodePagesWithReExecute("/Error/error/{0}");
app.UseExceptionHandler("/Error/error/500");

And added error handling action in ErrorController:

[Route("error/{code}")]
public IActionResult Error(int code)
{
    return new ObjectResult(new ApiResponse(code));
}

This is good for web api, but not for web pages. For api we want to return custom object (serialised as JSON) , but for UI we want to return custom view. I want to write something like

public IActionResult Error(int code)
{
     if(CalledFromApiClient())
     {
           return new ObjectResult(new ApiResponse(code));
     }
     else
        return View(“Error”);
}

The question is how to implement CalledFromApiClient?

I am thinking to keep all api controllers in api subfolder/namespace and use callstack to find was exception thrown from api controller or not. It should work, but it doesn’t look good.

Is any better way?