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Integration Guidelines for Protocols Supporting USDY on Mantle



USDY (US Dollar Yield Token): USDY is a tokenized note secured by short-term US Treasuries and bank demand deposits. USDY holders receive yield generated from the underlying assets in the form of increasing redemption value (accumulating token). USDY contract is an upgradeable (Transparent Upgradeable Proxy) ERC-20 token. To hold, send, and receive USDY, users should not be on the blocklist.

Note: an allowlist is implemented on Ethereum but does not apply on Mantle.


mUSD is the rebasing version of USDY, maintaining a consistent peg to $1. Interest is distributed via new token units. Users can swap freely between USDY and mUSD. A swapper UI will be available in October on

mUSD is heavily based on other rebasing tokens such as stETH. Users can acquire mUSD tokens by calling the wrap(uint256) function on the contract. While the price of a single USDY token increases over time, the price of a single mUSD token is fixed at a price of 1 Dollar, with yield being accrued in the form of additional mUSD tokens. Similarly when a user wishes to convert their mUSD to USDY they can call the unwrap(uint256) function, and receive their corresponding amount of USDY.

In order to determine the USD value of the USDY locked in the contract, mUSD will call into RWADynamicRateOracle.sol in order to fetch the current price.

Because mUSD is the rebasing variant of USDY the same transfer restrictions for USDY are also applied to the mUSD token in the beforeTransfer(address,address,uint256) hook.

mUSD rebases daily at 12:00am GMT.

USDY Oracle (RWADynamicRateOracle)

The RWADynamicRateOracle contract is used to post price evolution for USDY on chain. This contract accepts a Range as input from a trusted admin, and will apply the following conversion to the lastSetPrice for a given range:

currentPrice = (Range.dailyInterestRate ** (Days Elapsed + 1)) * Range.lastSetPrice

There is a functionality within the contract that if a range has elapsed and there is no subsequent range set, the oracle will return the maximum price of the previous range for all block.timestamp > Range.end

Integrating USDY into Your Web3 Application

As users may hold USDY or mUSD, a good practice is to support both.

Let's assume a user holds mUSD and wants to supply to your USDY pool.

Option 1: Native integration

The user can directly use his mUSD to interact with your contracts. This means that your contracts will add an extra call to swap from mUSD to USDY before depositing the USDY in the pool.

Example of a native integration: Compound pool on

Curve unwrapped
The user can deposit stables (unwrapped)
Curve wrapped
...or stables lent into Compound (wrapped)

Option 2: Informative integration

When trying to supply mUSD, your app informs the user they need to swap to USDY before depositing to the pool: “To supply USDY, you must first swap your mUSD for USDY at

Example of an informative integration: wstETH on Balancer

Balancer guidelines
The user is informed on how to wrap/unwrap

SmartContracts details

  • rUSDY.sol - This contract serves as the backbone for an interest-bearing token where users can wrap and unwrap their USDY tokens to earn interest. It also includes features for access control and address management.
  • rUSDYFactory.sol - This is a factory contract that allows the deployment of upgradable instances of the mUSD token contract. It is managed by a guardian address, and the deployment process involves creating an implementation contract, a proxy admin contract, and a proxy contract for the token. The code is designed to facilitate the upgradeability of the mUSD token and includes functions for batched external calls.
  • RWADynamicOracle.sol - This contract is a dynamic Oracle that provides the price of USDY based on configured time ranges and daily interest rates. It also includes mechanisms for pausing and access control to manage the ranges and contract operation.
  • IRWADynamicOracle - This is an interface that sets a standard for any contract wishing to provide information about the price of RWA (Asset-Backed Real World Assets) or similar assets. Contracts that implement this interface must provide a getPrice() function that returns the current price of RWA. The interface does not contain implementation logic but simply establishes a common structure for communication with dynamic asset price oracles.


Legal Notice

These pages are provided solely to facilitate your understanding of certain key features and terms of USDY and its issuer, and is qualified in all respects by the Tokenized Credit and Security Agreement, your Subscription Agreement, the Borrowing and Lending Memorandum, and the Limited Liability Company Agreement of Ondo USDY LLC.

For the purposes of these pages, the capitalized term “Token” shall refer to the transferrable USDY token.

Neither these pages, nor any related links or discussions, nor any portion hereof or thereof, constitutes any offer to sell, or any solicitation of an offer to buy, any securities, including but not limited to USDY Tokens.

Neither these pages, nor any related links or discussions, nor any portion hereof of thereof, constitutes any representation, warranty or covenant on the part of Ondo Finance Inc., Ondo USDY LLC or any other person.

These pages and their links contain, and officers, agents or representatives of Ondo Finance Inc. or Ondo USDY LLC may from time to time make, "forward-looking statements". Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based only on current beliefs, expectations and assumptions. Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of the control of Ondo Finance Inc., Ondo USDY LLC and their respective officers, agents and representatives. Actual results and financial condition may differ materially from those indicated in the forward-looking statements. Therefore, you should not rely on any of these forward-looking statements.

Acquiring USDY Tokens is speculative and involves substantial risks. There can be no assurances that a USDY Token holder will not incur losses, including total loss of their investment in USDY Tokens.

The USDY Tokens are not offered OR SOLD, and will not be offered OR SOLD, in the United States or to US persons. In addition, the USDY Tokens have not been registered under the Securities Act of 1933, as amended (the “Act”) or the securities laws of any other jurisdiction, and may not be offered, sold or otherwise transferred in the United States or to US persons unless the securities are registered under the Act, or an exemption from the registration requirements of the Act is available. Additional limitations on transfer also apply.