Billionaire Elon Musk arrived on Capitol Hill Tuesday and learned about something new — budget rescissions, an obscure legislative tool that could bring legal heft to his federal budget slashing effort and enshrine the cuts into law.

Congressional Republicans looking for clarity over Elon Musk’s efforts to slash the federal government will get an opportunity to engage with Musk directly on Wednesday in a pair of meetings on Capitol Hill,

At a mostly friendly closed-door meeting, the billionaire carrying out President Trump’s bid to shrink the federal bureaucracy fielded queries about how senators could be more involved in the effort.