Robert Mueller is a stickler for the rules. The special counsel team he led was a leakproof box , his spokesman seldom spoke and his only public statements came in the form of indictments and court filings.

But on March 27, three days after Attorney General William Barr cleared President Trump of criminal wrongdoing in a misleading and incomplete summary of Mr. Mueller’s report on the Russia investigation, the special counsel felt compelled to protest. In a letter made public on Wednesday, just as Mr. Barr was preparing to testify before the Senate Judiciary Committee, the American public got its first glimpse of how the special counsel thinks and speaks about his work.

Mr. Mueller’s tone and tenor are remarkable — and a sharp rebuke to Mr. Barr.

“The summary letter the Department sent to Congress and released to the public late in the afternoon of March 24 did not fully capture the context, nature, and substance of this Office’s work and conclusions,” Mr. Mueller wrote in a letter addressed to Mr. Barr , whose characterizations of Mr. Mueller’s investigation have also come under fire by members of the special counsel’s team.

The special counsel notes in his letter that just a day after Mr. Barr’s effort to spin the findings of the investigation (which Mr. Trump crowed was a “Complete and Total EXONERATION”), Mr. Mueller raised “concern” about all the confusion and misreporting that the attorney general had caused.