Runtime/AgentCore/Tools/Builtin/GetCurrentTimeTool.cs

using System;
using System.Globalization;
using System.Threading.Tasks;
using Microsoft.Extensions.AI;
namespace OnDeviceAgent.AgentCore
{

    public sealed class GetCurrentTimeTool : AgentToolBase
    {
        public override string Name => "GetCurrentTime";
        public override string Description =>
            "Get the current local time and date. Use when the user asks the time or date (e.g. 'what time is it', " +
            "'지금 몇시야', '오늘 며칠이야'). Always call this; never state the time or date from your own knowledge.";

        public override AITool ToAIFunction(AgentToolContext context)
        {
            return AIFunctionFactory.Create(
                new Func<Task<string>>(() => RunGuarded(context, "{}", () =>
                {
                    var now = DateTimeOffset.Now;
                    var inv = CultureInfo.InvariantCulture;
                    // 12-hour form, parts spelled out so small models echo the digits verbatim instead of recomputing.
                    return Task.FromResult("It is " + now.ToString("h:mm tt", inv) +
                        " on " + now.ToString("dddd, MMMM d, yyyy", inv) +
                        // "%h": a single-char custom format must be prefixed with '%', else .NET reads a lone
                        // "h" as a (nonexistent) STANDARD specifier and throws FormatException.
                        ". Report exactly hour=" + now.ToString("%h", inv) + " minute=" + now.ToString("mm", inv) +
                        " " + now.ToString("tt", inv) + "; keep these digits unchanged.");
                })),
                name: Name,
                description: Description);
        }
    }
}