Recomputes tokenized-vault conversions from a declared total_assets and total_supply, applying the rounding direction ERC-4626 mandates for each function and showing you which direction produced each number and what the opposite direction would have given. Also computes a deposit-then-redeem round-trip loss bound, the exchange-rate drift between two declared snapshots, and a declared fee. Every quantity is exact uint256 integer arithmetic, the same integer semantics Solidity uses. There is no floating point anywhere in it.
ERC-4626 mandates a rounding direction per function, and the reason is stated in the standard's own security considerations: it is considered most secure to favour the vault over its users, so amounts issued to a user round down and amounts a user must supply round up. Getting exactly one of those backwards is how a vault quietly leaks value, one wei at a time, which is why this tool reports each direction separately rather than a single verdict.
What it cannot tell you: whether the numbers you typed match any deployed vault, whether that vault's own implementation applies these directions, whether a rate change between two snapshots came from yield, a loss, a donation or an attack, or whether the fee basis points you declared are what anyone actually charges. It never fetches on-chain state and is never a party to a transaction. A round-trip loss or a zero-share mint reported here is a property of the numbers you supplied under the standard's arithmetic, not an audit of a deployment.