This tool is free, reads any address and asks for no signature. What it costs is a server.
At the top of the page there is a donation address and how much has come in this calendar month — it starts at zero again on the first. The chain is checked once an hour, so something you send shows up with the next check rather than right away.
$50 a month is what the site costs to run. Below that I cover the difference out of referral fees. $100 is the stretch: it pays for the time that goes into support and development.
USDC on Base or USDG on Robinhood. Nothing is expected, and nothing in the tool changes if you send something — there is no account, nothing is unlocked, and your numbers look the same either way.