On the economic side, the Tokyo summit was at best a modest success. But it did produce one substantive event: ratification of a proposal made by Treasury Secretary James A. Baker III that calls for stepped-up coordination of internal economic policies.

Under the agreement -- still on paper -- the seven summit nations would compare a long list of their economic indicators, including exchange rates. And if they get out of line with each other, the seven promise to make "best efforts" to get them back in line. As necessary, they would intervene in foreign exchange markets to keep exchange rates stable.

This may sound like pie in the sky -- and, indeed, there are skeptics who say that major nations such as the United States or Japan won't shift gears merely to satisfy the demands of their partners. If, in fact, such a mutual surveillance exercise is to be brought off, it would imply subordination of national interests from time to time in order to assure global prosperity.

It also means scrapping the present system, in which exchange rates are free to float in foreign exchange markets. Presently, speculators are often able to decide what a dollar, or the German mark, or the Japanese yen should be worth.

Baker told reporters the other day that "the proof of the pudding is in the eating. The proof of the Tokyo mechanism is in its implementation. We have to make it work, and we will only make it work if there is good faith and a cooperative spirit on the part of the countries involved."

In other words, having agreed in Tokyo that stability in exchange rates is desirable, and that to get such stability will require government involvement beyond what many of them -- including the Reagan administration -- had ever been willing to undertake before, the seven leaders now must demonstrate that there is the political will to do the job.

How can that political will be marshalled? Who will blow the whistle if, say, the U.S. budget deficit is too big, or the Japanese trade surplus is overwhelming the international system? These and related questions are scheduled to be explored at a privately sponsored meeting June 28-30 in Zurich among members of Parliaments and central bankers from Europe, Japan and the United States.

The Zurich meeting is the brainchild of two young Washington political consultants, David Smick and Richard Medley, who promoted a Washington meeting last November on behalf of Sen. Bill Bradley (D-N.J.) and Rep. Jack Kemp (R-N.Y.). That session highlighted the view of a heavily academic audience that the time had come for "target zones" -- a deal through which major nations agree to keep their exchange rates within stipulated, fairly fixed confines.

Their Zurich promotion is oriented less to economists, and more to politicians and central bankers who will have a role in shaping the political consensus needed to make Baker's proposal in Tokyo come alive. Its promoters hope the Zurich session takes on a quasi-official status.

Baker, who spoke briefly at the November meeting, has as yet made no formal commitment to go to Zurich. But it is almost certain that both Baker and Deputy Secretary Richard Darman will attend the meeting, and that Baker also will deliver a major policy speech at a joint session, the same weekend, of the American Chamber of Commerce and other American groups located in Switzerland.

The Smick-Medley Zurich meeting has already attracted other "star" players, including Hans Tietmeyer and Toyoo Gyoten, in charge of international finance matters for the German and Japanese ministries of finance, respectively; Miohel Camdessus, head of the Central Bank of France; Geoffrey Littler, permanent secretary of the British Treasury; Karl Otto Poehl, president of the German Bundesbank; Dutch Finance Minister H. O. Ruding, chairman of the Group of 10; and Jacques Attali, counselor to French President Francois Mitterrand.

In a paper prepared for Reagan administration officials, Smick and Medley contend that by the time of the Zurich meeting, the world will be confronted by three problems: a potential international trade war; an economic outlook less favorable than was claimed in Tokyo (both Japan and West Germany are expected soon to revise downward recent GNP projections); and an unsolved Third World debt problem.

"As far as we know, this gathering is currently the only realistic, nonofficial counterthrust to the protectionist firestorm now raging through the industrialized world. . . . In short, the upcoming Zurich event is the logistical next step after Tokyo," they said in the strategy paper.

One can wonder how much a private session -- even if star-studded and complete with a Baker appearance -- can accomplish on issues as complex as these. Smick and Medley recall that Maynard Keynes used private gatherings to build support for the new international monetary system launched at Bretton Woods in 1944. And when Bretton Woods finally unravelled three decades later, they say outside pressure accelerated the decision to abandon fixed for floating rates.

Clearly, interest has been growing in the future course of international economic cooperation ever since Baker's coup with the Group of 5 at the Plaza Hotel last September. Baker, supported by a bipartisan group in Congress, understood it had become necessary to abandon the Reagan administration's slavish devotion to a noninterventionist ideology. The manner in which Baker has reclaimed leadership for the United States on the international scene is considered by America's Asian and European partners as a hopeful portent for global economic recovery.

Smick and Medley see their Zurich session as a catalyst for a new international monetary system, "the beginning of 'the new internationalism.' " There may be a little -- but understandable -- exuberance in these words, but there can be no denial that their timing for the Zurich session is superb.