Add ITool + ToolRegistry + GetCurrentTimeTool

backend/Tools/GetCurrentTimeTool.cs

@@ -0,0 +1,20 @@
+using System.Text.Json;
+
+namespace backend.Tools;
+
+public class GetCurrentTimeTool : ITool
+{
+    public string Name => "get_current_time";
+    public string Description => "Returns the current UTC time as an ISO-8601 string.";
+    public bool RunsDuringResponse => false;
+
+    public JsonElement ParameterSchema { get; } =
+        JsonDocument.Parse("""{"type":"object","properties":{},"required":[]}""").RootElement;
+
+    public Task<ToolResult> ExecuteAsync(ToolInvocation invocation, DeviceContext device, CancellationToken ct)
+    {
+        var now = DateTimeOffset.UtcNow.ToString("yyyy-MM-ddTHH:mm:ssZ");
+        var output = JsonDocument.Parse($$"""{"now":"{{now}}"}""").RootElement;
+        return Task.FromResult(new ToolResult(output));
+    }
+}