Understand any hook before you dive in.
Uniswap v4 pools can run a hook: custom code on every deposit, withdrawal or swap. Some charge fees, some lock liquidity, some take a cut. Paste a hook's address and Fathom shows what it's allowed to do.
Three depths
Every hook starts at 100. Each power it has over your money makes the water shallower.
Deep water
80 to 100. The hook watches or tunes the pool but can't touch your funds.
Shoals
50 to 79. It can set fees, gate who joins, or change amounts. Know what you're agreeing to.
Reef
Under 50. It can take from swaps or withdrawals, or lock liquidity. Read every line.
What a sounding reads
Permissions
In v4, what a hook may do is written into the last bits of its address. Fathom reads all 14 and explains each in plain words.
Who's in control
Can the code be swapped out? Is the owner one wallet, a multisig or a timelock? Can they raise the fee?
Where it's used
The pools running the hook and the liquidity in them, so you know how much is riding on it.