The race is on for one of the most prized development sites in Greater Boston, if not the country.

You wouldn’t know it though.

A slew of major builders last week filed proposals to redevelop the Volpe Center in Cambridge and gain access to 14 acres of buildable land in the heart of Kendall Square, a rare chance to reshape a big chunk of one of the nation’s richest real estate markets.

But the federal agency that will pick a winner for the site — likely by the end of the year — is conducting the contest under a near total “cone of silence,’’ sharing little about what they’d like to see at the Volpe or what developers are pitching there. And that’s frustrating many in Cambridge, where civic debate and in-depth analysis is practically a way of life.

“It’s like they’re from some different time,’’ said City Council member Nadeem Mazen. “It’s ‘We’re the federal government and we’re going to do what we want.’ ’’

City staff and council members spent months last year trying to update zoning on the site — which today houses a ’60s-era concrete tower surrounded by acres of fenced-off grass and parking lots — to reflect what they’d want today. But they gave up amid a jumble of competing demands for affordable housing, open space, and other civic needs. They’re starting again, with the hope of finalizing plans next year after a developer is picked.

“There will be many opportunities to influence this,’’ said Iram Farooq, assistant city manager for community development.

But it’s tough to even start the conversation without a better sense of what the General Services Administration wants, what developers have in mind, and the economics of a project that will likely run north of a billion dollars, said City Council member Craig Kelley. How do you set open space requirements, for example, without knowing what sort of security perimeter a federal building like the Volpe might need, or what retail might be possible without an idea of the site’s layout?

“The lack of information really hinders our ability to talk with each other and explain to the community what we think is going on,’’ Kelley said. “It’s going to make things harder for everyone.’’

The GSA, the federal agency that’s managing the project, has met numerous times during the last two years with Cambridge city staff, Farooq said. But they’ve shared few specifics about what they want, beyond the requirement of a roughly 400,000-square-foot office building to replace the existing Volpe Center.

Last year, the GSA required interested developers to meet with city staff, and 13 firms did. But since then they’ve shared little about what they might be planning, citing rules that shield the federal procurement process from public records laws. When final proposals came due last week, the agency would only say they got “multiple responses.’’

“Review of the responses is underway and on schedule,’’ the GSA said in a statement. “The government is pleased with the quantity and quality of the respondents who submitted proposals.’’

City officials and others familiar with the bidding say the names they’ve heard are a who’s-who of deep-pocketed developers, with experience in Boston and, in many cases, Kendall Square. Among them: Alexandria Real Estate Equities; a partnership of Biomed Realty and Longfellow Real Estate Partners; Boston Properties; a team of HYM Investments and Tishman Speyer; MIT Investment Management Co.; Related Beal; and Skanska USA.

The developers involved all declined comment, citing the GSA’s desire for privacy. And the agency wouldn’t share their proposals. But the GSA is vetting them thoroughly.

A copy of the request for proposals obtained by the Globe asks each team to prove deep experience and financial resources, enlist three separate design firms it could potentially partner with, and submit a preliminary plan for a 390,000-square-foot building that it would build to replace the Volpe before getting the right to develop the rest of the site.

It’s a lot to ask, said David Begelfer, CEO of real estate trade group NAIOP Massachusetts. But it could come with a hefty reward. Office rents in Kendall Square are among the highest on the East Coast, and the chance to build there should draw ambitious projects from big-name builders.

“The center of Kendall Square is where people want to be,’’ he said. “It’s going to be an extraordinarily competitive bidding process.’’

Still, even a project this rich has its limits, said Alexandra Lee, executive director of the Kendall Square Association. Cambridge in recent years has layered new requirements on developers for affordable housing, startup space, energy efficiency, and more. The expectations at Volpe are even higher; last year some in the city were pushing for half the site to be set aside as open space. And then there are the federal government’s needs.

“All of that costs money, so what are the trade-offs,’’ Lee said. “One has to talk about trade-offs when one talks about Volpe.’’

It’s hard to do that without knowing specifics, said City Council member Dennis Carlone, which is why it makes sense to write zoning before a developer signs on. That way they can design their projects, and budgets, accordingly. That missed opportunity highlights the disconnect between a closed-off federal facility set back behind a fence and the business hub of a city that prides itself on collaboration and debate.

“Let’s face it, they want to be in Cambridge, near MIT. But they really want to be alone,’’ Carlone said. “They want to be a castle on a hill in a city where there are no hills. It’s odd.’’

Tim Logan can be reached at tim.logan@globe.com. Follow him on Twitter at @bytimlogan.