Depends. #1 is your FAA certificate in your pocket. That is required and may alleviate the inquisitions from LE officers. Everyone will have an opinion on this so here's what I've carried since 2015:
A folder, indexed with tabs so each section can be easily located:
Copies (never originals) of my FAA license, local business license (if required by ordinance), FAA N# registration for all my aircraft, insurance police/certificate, driver's license (cops will always do a wants and warrant NCIC check and having my license info in their hands will facilitate it). If they want to see the actual driver's license then I'll get out my wallet, and copies of Airspace Authorizations, whether long form FAA or the LAANC quickies you can get from Skyward when flying in controlled airspace.
The folder is in my briefcase so is always in my work SUV. I was working in Phoenix (very close to Sky Harbor-class Bravo) earlier this year, a couple of young cops stopped and just watched me for a while. After I landed they came over and chatted about drones; one of them owned a P4 and we got to talking.
Being a retired cop, I do understand the police mentality. In a very casual tone the P4 owner mentioned I was very close to the airport. I replied with, yes sir, I do have FAA authorization, would you like to see it? His reply was amusing, "you know, I've never seen one, may I see it? " A very polite way to ask to see my airspace authorization. Point of the story is have an embarkation checklist, to ensure nothing is forgotten before u leave home.
Anyway, that's my two cents. Are you required to have all this crap on you? Not really but I found it makes life easier and shows whoever asks, you are a professional operating a business, not some "yahoo with a drone." I work a lot of construction sites so vest & hardhat are also a must have.