Can a vault’s redemption preview be used directly as a price?
“Closely reflects the outcome of this operation” doesn’t mean it’s suitable as a price reference for another application.
The ERC-4626 vault standard in the $ETH ecosystem cautions that preview methods aim to approximate the result of an operation under current conditions. But on-chain conditions can change, so these return values aren’t always suitable for use as price oracles—inputs that provide prices to other programs.
For example, an application that uses the value of vault shares to determine borrowing limits shouldn’t assume that a preview’s reported redemption amount is protected against short-term price manipulation. To assess whether it’s suitable, you also need to examine the specific calculation method, how its inputs can be changed, and how the receiving application handles unusual values. This is a conditional risk analysis; it doesn’t allege that any particular vault is under attack.
The standard allows another type of conversion query to use more robust calculations, such as a time-weighted average—but that doesn’t guarantee that every vault implements it. When reading integration documentation, first ask which method is used and why it’s suitable for that purpose. Don’t equate “more precise preview” with “more reliable price.”
Source: https://eips.ethereum.org/EIPS/eip-4626
“Closely reflects the outcome of this operation” doesn’t mean it’s suitable as a price reference for another application.
The ERC-4626 vault standard in the $ETH ecosystem cautions that preview methods aim to approximate the result of an operation under current conditions. But on-chain conditions can change, so these return values aren’t always suitable for use as price oracles—inputs that provide prices to other programs.
For example, an application that uses the value of vault shares to determine borrowing limits shouldn’t assume that a preview’s reported redemption amount is protected against short-term price manipulation. To assess whether it’s suitable, you also need to examine the specific calculation method, how its inputs can be changed, and how the receiving application handles unusual values. This is a conditional risk analysis; it doesn’t allege that any particular vault is under attack.
The standard allows another type of conversion query to use more robust calculations, such as a time-weighted average—but that doesn’t guarantee that every vault implements it. When reading integration documentation, first ask which method is used and why it’s suitable for that purpose. Don’t equate “more precise preview” with “more reliable price.”
Source: https://eips.ethereum.org/EIPS/eip-4626