URL       = "https://b24-ar17wx.bitrix24.by/rest/1/h0m...";
    ChatID    = "chat" + "2422";
    MessageID = "3850";

    Result = OPI_Bitrix24.MarkMessageAsReaded(URL, ChatID, MessageID);

    URL       = "b24-ar17wx.bitrix24.by";
    Token     = "4dee2c68006e9f06006b12e400000001000...";
    UserID    = 10;
    MessageID = "4286";

    Result = OPI_Bitrix24.MarkMessageAsReaded(URL, UserID, MessageID, Token);