Sen. Chuck Grassley (R-Iowa) wants more details about John Kerry's personal finances and how the Biden climate envoy is avoiding conflicts between his official duties and private investments.

The big picture: Grassley, the top Republican on the Senate Judiciary Committee, sent a letter to Secretary of State Antony Blinken on Monday seeking more information after Axios revealed new details about Kerry's lucrative work in finance and energy investing after he completed his tenure as secretary himself.

• "The operation of good government requires faithful adherence to ethical rules," Grassley wrote. "It’s unclear exactly what matters Mr. Kerry has been barred from working on and whether he has received any waivers for specific matters that he would otherwise be recused from."

Between the lines: As Axios reported Friday, Kerry drew a $5 million salary from Bank of America last year and brought in hundreds of thousands more in speaking fees and consulting income.

• Some of his former clients do significant business in the energy and environmental space, over which Kerry is now poised to exert significant policy influence as special presidential envoy for climate.
• Kerry also has pressed major financial institutions to collaborate on efforts to address global climate change.
• According to a Politico report in March, that included entreaties to Brian Moynihan, Bank of America's CEO.

The intrigue: The State Department told Axios last week Kerry has signed a Biden-imposed ethics pledge barring him from participating in specific official actions affecting his former clients and employers.

He's also bound by federal ethics laws restricting that activity.

• Grassley wants to know precisely what Kerry is recused from doing, and whether any of those rules have been waived.
• The senator's letter also requests "all records, including memoranda, emails and other similar documents, relating to all evaluations of potential, apparent and/or actual conflicts of interest."
• The department declined to comment about the letter.