Stephen K. Bannon isn’t the only person offering a candid assessment about the Trump administration in the upcoming book “Fire and Fury: Inside the Trump White House” by Michael Wolff. (Bastien Inzaurralde/The Washington Post)

Michael Wolff says he didn’t exactly trick President Trump while he was researching his scathing overnight bestseller, “Fire and Fury.”

“Whether he realized it was an interview or not, I don’t know, but it certainly was not off the record,” Wolff said Friday on NBC’s “Today” show, describing his conversation with Trump, who claims he gave the infamous author “zero access.”

As to whether he misled anyone about what he was doing hanging around the West Wing, Wolff’s words may go down in journalism history: “I said whatever was necessary to get the story.”

Wolff, of course, has a reputation for “busting embargoes and burning sources by putting off-the-record comments on the record,” as one assessment put it.

Even so, even people who should know better about spilling their guts to a reporter often don’t.

Michael Wolff “said whatever was necessary to get the story.” (Brendan Mcdermid/Reuters)

Last year, the president’s newly named communications director Anthony Scaramucci apparently thought he was off the record when he profanely trashed his White House colleagues to journalist Ryan Lizza, then of the New Yorker. Lizza wrote it up, and Scaramucci flamed out.

Last August, White House chief strategist Stephen K. Bannon was ousted shortly after the American Prospect’s Robert Kuttner quoted him blasting the Trump administration’s economic and foreign policy. Kuttner later said he was stunned that Bannon (who later claimed the interview was not the cause of his departure) never bothered to make the conversation off the record.

And a few years ago, Wolff himself neglected to mention to Ben Smith that a dinner he had invited the BuzzFeed editor in chief to was off the record. Smith wrote a story that embarrassed Uber executives, and Wolff in turn wrote a column that chided Smith, but also blamed himself for not being explicit about the ground rules.

Some people never allow for the possibility of such mishaps.

“My personal practice is to speak on the record or keep my mouth shut,” said Jonathan Landman, editor in charge of opinion columns at Bloomberg View and a former high-ranking New York Times editor.

Landman claims no moral superiority. He knows that there are plenty of valid justifications for people speaking off the record or on background, the latter meaning that information can be used but without the source’s name. (Wolff wrote that he used “deep background,” which allows the use of information, as if it came from an omniscient observer, not attributed to anyone.)

“For me,” Landman told me by email, “the reasons have much more to do with self-discipline than high principle.”

Janet Malcolm, in “The Journalist and the Murderer,” caustically observed that reporters don’t make dependable friends. In her case study of journalistic ethics, she explored the interactions between author Joe McGinniss and the subject of his true-crime classic, “Fatal Vision,” convicted murderer Dr. Jeffrey MacDonald, who felt betrayed by reporting which he mistakenly thought would exonerate him.

“Something seems to happen to people when they meet a journalist, and what happens is exactly the opposite of what one would expect,” Malcolm wrote. “One would think that extreme wariness and caution would be the order of the day, but in fact childish trust and impetuosity are far more common.”

Of course, when journalists do become their sources’ friends, other problems may arise.

And ethical journalists honor their commitments to their sources — to the point of being willing to go to jail to protect confidentiality. But that assumes a true agreement has been reached.

Jim VandeHei and Mike Allen, on the news website Axios, called Wolff’s “liberties with off-the-record comments . . . ethically unacceptable to nearly all reporters.” But, they granted, they do “have the effect of exposing Washington’s insider jokes and secret languages, which normal Americans find perplexing and detestable.”

VandeHei and Allen then slyly confirmed some of Wolff’s reporting: “In the past year, we have had many of the same conversations with the same sources Wolff used. We won’t betray them, or put on the record what was off.” Still, they wrote, certain lines in Wolff’s book rang unambiguously true; they provided a list.

So, if “off the record” really means that what a reporter is seeing and hearing can’t be used in any form, ever, that’s a high bar. But it’s when the agreement is implied, not nailed down, that most screw-ups (and sometimes the juiciest stories) result.

The late Michael Hastings decided not to observe implicit rules when he described how Army Gen. Stanley A. McChrystal and his staff mocked top civilian officials, including Vice President Joe Biden. After Hastings’s Rolling Stone report was published in 2010, President Barack Obama fired his top U.S. military commander in Afghanistan.

Hastings later bashed other military reporters for ceding their ability to tell the unvarnished truth by trading it for access. “They go on these trips with McChrystal and they get to see all this cool stuff,” he told the Guardian, “and they completely drink the Kool-Aid.”

Now along comes Wolff, whose abundant faults don’t include drinking the Kool-Aid.

“One of the things that’s unnerving about Michael is he’s loyal only to the story,” the former Hollywood Reporter editor Janice Min said in a New York Times interview.

He said and did “whatever was necessary,” as Wolff put it.

The lesson is there for the taking but certain to be ignored again and again: Let the speaker beware.

For more by Margaret Sullivan visit wapo.st/sullivan