President Reagan headed home today from his longest overseas journey, basking in the glow of a congenial economic summit that outwardly went well but whose tangible results are much in doubt.

President Reagan, appearing chipper and confident at a news conference before he left for Washington, called the summit the "most successsful" of the six he has attended. He said that the seven industrialized democracies were unified as never before in fighting terrorism and claimed that the economic progress of the summit members reflected "a rising tide of prosperity that demonstrates the wisdom of the free-market policies we have pursued."

Despite the self-congratulations, U.S. and allied officials acknowledged that it was uncertain what the ringing declarations adopted here would accomplish. One Canadian official, strongly supportive of the summit declaration on terrorism, said, "It remains to be seen whether we can translate these fine-sounding words into actual deeds."

Even before the ink was dry on what Secretary of State George P. Shultz called "a terrific statement" opposing state-supported terrorism, Japanese and French officials were interpreting the list of specific measures called for in the resolution as discretionary, meaning that each nation could decide for itself what to do.

British Prime Minister Margaret Thatcher, Reagan's staunchest ally on this and many other issues, said yesterday that the actions specified in the resolution applied only to Libya and that neither Britain nor the United States interpreted it as carte blanche to take military actions.

Similar reservations were expressed about other declarations adopted at the 12th economic summit, even those that pleased the Reagan administration most.

Treasury Secretary James A. Baker III called the summit "a very substantive economic meeting," but Baker and others said it would take many months, perhaps a year, to see whether the international currency reforms approved here will have an impact on the huge U.S. trade deficit.

Nonetheless, Baker's aggressive initiative for currency reform made him the dominant figure among the finance ministers at this summit.

A wait-and-see attitude also developed here about another resolution adopted with great fanfare, a declaration on nuclear safety inspired by the accident at the Soviet reactor at Chernobyl.

The resolution, pushed by West German Chancellor Helmut Kohl, expressed "satisfaction" that the Soviets had agreed to talk to the International Atomic Energy Agency about the accident.

But U.S. officials said they were uncertain whether the Soviets will take the next step and allow on-site inspection of Chernobyl and similar graphite-moderated reactors.

Despite these reservations, satisfaction was expressed in the U.S. delegation with Reagan's performance at his sixth economic summit, which was noticeably less acrimonious than some of his past meetings with leaders of the industrialized democracies.

Reagan was described by one aide as "an old hand at this now, well accustomed to the world stage and familiar with the views and approaches of the other leaders."

From the U.S. point of view the unity at Tokyo represented a general prosperity associated with the drop in world oil prices, lowered interest rates and reduced inflation.

A senior U.S. official said this summit also went more smoothly because U.S.-French discussions were less acrimonious than usual. He attributed this in part to the desire of Socialist French President Francois Mitterand to show that he could get along with his political rival, French Prime Minister Jacques Chirac, a conservative.

Beyond the summit, administration officials were more restrained in their evaluation of the 13-day Reagan journey, which began with an overnight stay in Los Angeles, included two days in Honolulu and a three-day trip to Bali, Indonesia, where the president met with foreign ministers of the Association of Southeast Asian Nations.

Reagan's most controversial moments on this 22,000-mile trip involved the period before the summit, beginning with a speech he gave in Washington the day before his departure in which he repeatedly used the words "winds of freedom" to describe his view that democracy is spreading throughout the world.

While in Hawaii the president caused some consternation in the Philippines by telephoning deposed Filipino president Ferdinand Marcos.

The "winds of freedom" theme received some more buffeting in Indonesia, where President Suharto drew attention to the lack of civil liberties in his country by refusing admission to two Australian broadcast correspondents traveling on the White House press plane because an Australian newspaper had accused Suharto of favoring family members and business associates with lucrative government contracts.

"Indonesia was supposed to be a rest stop," said one official. "It didn't turn out that way. The 'winds of freedom' business wouldn't have caused a stir if Suharto hadn't drawn attention to it by his attitude to the press."

The "winds of freedom" phrase, for which no one was willing to take credit, and which Reagan did not mention today, was suggested by a junior national security official and quickly adopted by a White House eager to find an overarching theme for the trip.

Sources said it was originally intended to apply to the crosscurrents of economic democracy flowing through Europe, the United States and Japan at the summit.

If U.S. officials caused more controversy than they intended in Hawaii and Indonesia, they were pleasantly surprised by developments in Tokyo, where they had thought approval of a resolution on terrorism that identified Libya by name was unlikely.

Prospects for such identification appeared so dim that White House spokesman Larry Speakes expressed satisfaction with a much weaker resolution.

But Reagan was rescued, as he has been at previous summits, by Thatcher, who successfully fought for a tougher resolution.

"Maggie just wasn't going to settle for an empty declaration," said a U.S. official admiringly.

Thatcher played a similar role in London in 1984, in an antiterrorist resolution then hailed by U.S. officials, including Reagan and Shultz, as an effective denunciation of terrorism. Like the resolution approved in Tokyo, that declaration outlined a number of specific measures designed to cope with state-sponsored terrorism.

And like many statements of the leaders at the summit in their 12 years of meetings, the 1984 resolution produced no tangible results. U.S. officials, basking in the glow of their own evaluations, are hoping it will be different this time