More than 30 privacy and civil liberties organizations are challenging Director of National Intelligence James Clapper to uphold the promise he made Tuesday to increase transparency in the intelligence community.

Specifically, they are asking Clapper to provide more information about how many Americans are “incidentally” spied on in the course of foreign intelligence gathering under Section 702 of the Foreign Intelligence Surveillance Act.

“Disclosing this information is necessary, we believe, to enable informed public debate in advance of any legislative reauthorization efforts in 2017,” said the letter from the Brennan Center for Justice, the Electronic Frontier Foundation, the Government Accountability Project, and more than two dozen other organizations.

Clapper announced a new 16-page plan to share more information on Tuesday, and said he would be hosting a live Tumblr chat about it in the coming weeks.

“We want to challenge the DNI to put his money where his mouth is and give us this really important information, and to find a way to make this information available,” Elizabeth Goitein, co-director of the Brennan Center for Justice’s Liberty and National Security Program, told The Intercept.

Section 702, the NSA claims, authorizes two massive communications surveillance programs: PRISM and Upstream. As long as communications are reasonably believed to belong to foreigners and are swept up in the pursuit of foreign intelligence, the NSA says they’re fair game.

PRISM sucks up hundreds of millions of Internet communications of foreign intelligence “targets” directly from providers’ databases — Facebook messages, emails, Skype calls. But it also sweeps up communications of people who talk to those targets and some unrelated communications —“incidental” collection, which includes communications of American citizens.

The Upstream program vacuums up communications traveling in and out of the U.S. via fiber-optic cables maintained by telecoms like Verizon and AT&T. Those communications are supposedly filtered and searched using specific “selectors.” Selected communications are sent into databases where they can be accessed by other agencies, like the FBI. The FBI is allowed to search Upstream databases for indicators of criminal activity in America without a warrant, even though the collection wasn’t meant to include domestic data — a “backdoor search.”

Despite efforts by lawmakers, activists, and the Privacy and Civil Liberties Oversight Board, no one knows just how many of Americans’ calls, texts, and social media messages end up in the foreign intelligence dragnet. Nor do we know how often the FBI searches for American persons in the database, or the policies mandating how agencies have to notify people when information swept up in 702 collection will be used against them in court.

Goitein told The Intercept the letter is part of “gearing up” for a public debate on Section 702, which sunsets in December 2017. “While that seems like a long way away,” she says, “the USA Freedom Act was a 2-year-long effort,” kickstarted by Snowden’s revelations. “The American public must have the data necessary to evaluate and weigh these official claims,” says the letter.

“The Brennan Center’s questions are clearly important to better understanding the scope of surveillance under FISA Section 702,” writes Keith Chu, a spokesperson for Sen. Ron Wyden, D-Ore., who has repeatedly asked Clapper about the extent of 702 surveillance, along with former Sen. Mark Udall, D-Colo.