let t_descr ~ni:d_ninfo ~ci:d_cinfo =
    t_record
      [| pack (Signature.Str_descr.t d_ninfo);
         pack (t_list (t_tuple [| Key.t_call_id_packed_descr;
                                  pack (t_tuple [|
                                          pack (t_option d_cinfo);
                                          pack (Signature.Str_descr.t d_ninfo);
                                        |])
                               |]));
         pack (t_hashtbl_unchanged_hashs (Descr.str Hkey.descr) d_ninfo);
      |]