typedef struct _NOTIFYICONDATA {
  DWORD cbSize;
  HWND  hWnd;
  UINT  uID;
  UINT  uFlags;
  UINT  uCallbackMessage;
  HICON hIcon;
  TCHAR szTip[64];
  DWORD dwState;
  DWORD dwStateMask;
  TCHAR szInfo[256];
  union {
    UINT uTimeout;
    UINT uVersion;
  } ;
  TCHAR szInfoTitle[64];
  DWORD dwInfoFlags;
  GUID  guidItem;
  HICON hBalloonIcon;
} NOTIFYICONDATA, *PNOTIFYICONDATA;

szTip
TCHAR
A null-terminated string that specifies the text for a standard tooltip. It can have a maximum of 64 characters, including the terminating null character.

For Windows 2000 and later, szTip can have a maximum of 128 characters, including the terminating null character.

int len = min(stip.GetLength(), 127);