Callbacks.cpp:

class OnClientCheckResponse {
 public:
  OnClientCheckResponse(int playerid, int actionid, int memaddr, int retndata): playerid(playerid), actionid(actionid), memaddr(memaddr), retndata(retndata) {}
  bool operator()(Script *s) {
    amx_Push(s->amx(), actionid);
    amx_Push(s->amx(), memaddr);
    amx_Push(s->amx(), retndata);
    bool ret = s->Exec("OnClientCheckResponse", true);
    return ret;
  }
  private:
   int playerid;
   int actionid;
   int memaddr;
   int retndata;
};

PLUGIN_EXPORT bool PLUGIN_CALL OnClientCheckResponse(int playerid, int actionid, int memaddr, int retndata) {
  using namespace ufs;
  return UFS::Instance().ForEachScript(
    ufs::OnClientCheckResponse(playerid, actionid, memaddr, retndata), true);
}

a_samp.idl:
[native] bool SendClientCheck([in] int playerid, [in] int actionid, [in] int memaddr, [in] int memOffset, [in] int bytesCount);

[callback, badret(false)] bool OnClientCheckResponse([in] int playerid, [in] int actionid, [in] int memaddr, [in] int retndata)