(CNN) The news broke late Tuesday night: Special counsel Robert Mueller agreed to come to Congress and testify on July 17 about his nearly two-year long investigation into Russia's attempts to interfere in the 2016 election and any possible collusion between the Trump campaign and the Russians.

Mueller's testimony is a BIG deal -- especially since he made clear in a brief statement last month that he preferred that to be his last public word on the matter. His testimony represents Democrats' best chance to air some of the more damning elements of the Mueller report -- and to ask questions that only the special counsel can answer.

In each episode of his weekly YouTube show, Chris Cillizza will delve a little deeper into the surreal world of politics. Click to subscribe!

So, what should members of Congress ask Mueller? Here's seven good questions I'd like to see asked.

1) What did your report find?

Yes, I know the 448-page Mueller report has been available for public consumption since mid-April. And that media outlets -- CNN included -- have pored over it and reported out lots and lots of the details contained in it. But, I still think the average person has only the vaguest sense of what Mueller concluded -- and why he concluded it. A public recitation of his findings -- or even the toplines -- coming from the man himself would be a useful act of public education. If Mueller simply, in his own words, detailed the 10 major takeaways from the report -- with examples cited for why he concluded what he did -- I think we would all be better off. It might not change much in terms of how people feel about his report but at least we might have a more fact-based debate.

2) Why didn't you offer a recommendation on charging Trump with obstruction?

One of the central disagreements -- or, at least, questions -- in the wake of Mueller's report is why, after detailing a series of potentially obstructive behaviors by the President did he not offer a charging recommendation? Mueller's public statement seemed to make clear that he never even considered charging the President due to Justice Department guidelines that made clear that a sitting president can't be indicted. But, Attorney General William Barr, who made the decision after reading the Mueller report not to charge Trump, said that he had several conversations with Mueller in which the special counsel said the Justice Department precedent wasn't the singular reason he didn't charge Trump. So, which is it?

3) Did William Barr adequately summarize the conclusions of your report in the March summary letter he sent to Congress?

We know that Mueller sent Barr a letter following the release of Barr's summary lette r -- which he later said was more of a toplines from the report rather than a summary -- complaining that some of his findings were not properly described. Barr said that the concerns expressed by Mueller related solely to the way to the media covered the question of obstruction as detailed in the report. Is that correct? Or did Mueller also have issues with the way in which Barr presented the information?

4) Did you mean to put the onus on Congress to act on your conclusions?

In the report, Mueller writes this: "The conclusion that Congress may apply the obstruction laws to the President's corrupt exercise of the powers of office accords with our constitutional system of checks and balances and the principle that no person is above the law."

That line -- when coupled with Mueller's stated belief that he did not even consider charging Trump because of Justice Department precedent -- seemed to suggest that Mueller was laying out a sort of map or blueprint for how his conclusions could be used to underline an impeachment inquiry. Mueller is never going to answer whether or not he thinks Trump should be impeached but he might answer a direct question as to why he included those lines about Congress' ability to pursue the President on obstruction charges.

5) Was this probe illegal? If not, why not?

Again, this question is more about educating the public than about unearthing lots of new information. But Trump has repeatedly insisted over the past two years that the entire special counsel investigation was illegal because it was wholly built on a dossier compiled by former British spy Christopher Steele, who was being paid by Hillary Clinton and the Democratic National Committee. We know that's not true -- thanks to the Mueller report and former FBI Director James Comey's under-oath statements that the origin of the FBI counterintelligence operation came from a conversation that Trump campaign adviser George Papadopoulos had with an Australian diplomat in the summer of 2016. It's important, however, for the public to hear Mueller -- a man who spent 12 years as the head of the FBI, a role he was appointed to by a Republican president and a Democratic president -- explain in his own words why Trump's claims are simply false.

6) Can you explain the nature of your membership at Trump national golf club and the circumstances that led to your departure from the club?

Trump has cast this dispute as the basis for why Mueller was biased against him. In the Mueller report, the special counsel explained that he was a member of the club in Virginia, but he and his family weren't using it all that much. When he decided to leave, he inquired as to whether he could get back a portion of his membership dues. The club said he would be put on a wait list to get the dues back. The end. There's just no there here but because Trump has so fixated on the idea that he and Mueller have some sort of nasty history, it would be informative and instructive to hear Mueller explain how minor a matter this actually was and, in so doing, expose Trump's own tendency toward exaggeration and falsehood.

7) Are you and James Comey best friends? What is the nature of your relationship?