badrequest.cs

public IActionResult AddToAccount()
{
    var problem = new OutOfCreditProblemDetails
    {
        Type = "https://example.com/probs/out-of-credit",
        Title = "You do not have enough credit.",
        Detail = "Your current balance is 30, but that costs 50.",
        Instance = "/account/12345/msgs/abc",
        Balance = 30.0m,
        Accounts = { "/account/12345","/account/67890" }
    };

    return BadRequest(problem);
}
        
public class OutOfCreditProblemDetails : Microsoft.AspNetCore.Mvc.ProblemDetails
{
    public OutOfCreditProblemDetails()
    {
        Accounts = new List<string>();
    }

    public decimal Balance { get; set; }

    public ICollection<string> Accounts { get; }
}