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Caution Tokens

In the Vault, only fungible tokens (ERC-20) are handled, and within this broad category, there may exist various types of tokens that operate with unique algorithms or logics. However, among these diverse types, there are several tokens that require extra caution during trading. When trading a specific asset in the vault, it's safer to have a certain level of understanding of the asset's specifics.

Fee-on-transfer Tokens​

Fee-on-transfer tokens may exhibit discrepancies between the displayed exchange rate and the actual amount of MECA obtained after the deposit. The vault proceeds with exchanges based on the actual amount transferred. Fee-on-transfer tokens include transaction fees in the transferred amount, resulting in a lower actual transfer amount. The transfer fee of such tokens is separate from the fees required by the vault and is determined by the token contract.

Thus, this discrepancy is not an issue with the vault itself but rather a problem inherent to fee-on-transfer tokens, where the actual amount sent to the vault differs, causing differences in the displayed exchange rate during estimation. Similarly, the quantity of tokens actually acquired after the transaction may also differ from the displayed value or expectation. However, all of these are not problems originating from the vault.

Therefore, to avoid unintended trading losses through transactions in the vault, or even if unexpected outcomes have already occurred when trading a particular token in the vault, it is necessary to confirm whether the token is of this type. Additionally, it's crucial to be aware that such tokens may incur unexpected losses during trading, as the amount during transactions can change due to the token's internal formulas or logics.

Rebase Token​

Rebase tokens have the potential to cause several complex issues. Similar to fee-on-transfer tokens, when the quantity held by the vault changes due to transfers, whether before or after the transfer or after listing on the vault, the exchange rate is determined based on the quantity held by the vault at the last transaction. In this case, if the quantity decreases compared to the last balance, the exchange rate increases proportionally by the difference. Perhaps this would result in significant losses.

Since developers can write and deploy malicious code in smart contracts, in extreme scenarios, there could be cases where the storage is manipulated through ownership to facilitate MECA theft from the vault. In such cases, MECA theft can occur by repeatedly depositing assets into the vault, resetting the token balance in the vault, and re-depositing them.

Therefore, due to the practical difficulty of verifying whether any malicious content is present in a specific token contract, the vault implements uniform rules for tokens of the rebase type to prevent malicious scenarios. To achieve this, the balance of each token is separately checked. As a result, rebase tokens handled by the vault often incur losses with each transaction. Hence, careful trading is necessary, taking into account the correlation between the MECA exchange rate, the rebase timing of the token, and the held balance.