📝Contract Interactions

Market Membership

Enter Markets

Enable supplied assets as collateral. You must enter a market before you can borrow against it. You can enter multiple markets in a single call.

function enterMarkets(address[] memory mTokens) public returns (uint[] memory)

Parameter	Type	Description
mTokens	address[]	The list of mToken addresses to enter
returns	uint[]	An array of error codes per market (0 = success)

Solidity

Comptroller comptroller = Comptroller(0x...);

address[] memory markets = new address[](2);
markets[0] = address(mUSDC);
markets[1] = address(mWETH);

uint[] memory errors = comptroller.enterMarkets(markets);
require(errors[0] == 0 && errors[1] == 0, "enterMarkets failed");

---

Exit Market

Remove an asset from your collateral set. This will fail if you have an outstanding borrow in this market, or if exiting would make your position undercollateralized.

function exitMarket(address mTokenAddress) external returns (uint)

Parameter	Type	Description
mTokenAddress	address	The mToken to exit
returns	uint	0 on success, otherwise an Error code

---

Check Membership

Check whether an account has entered a specific market.

function checkMembership(address account, MToken mToken) external view returns (bool)

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Get Assets In

Get the list of markets an account has entered.

function getAssetsIn(address account) external view returns (MToken[] memory)

Parameter	Type	Description
account	address	The account to query
returns	MToken[]	Array of mToken addresses the account has entered

---

Liquidity & Liquidation

Get Account Liquidity

Calculate an account's available borrowing capacity (or shortfall if underwater). Values are denominated in USD with 18 decimals of precision.

function getAccountLiquidity(address account) public view returns (uint, uint, uint)

Parameter	Type	Description
account	address	The account to evaluate
returns	(uint, uint, uint)	(error, liquidity, shortfall)

• If liquidity > 0: the account can borrow up to this USD value

• If shortfall > 0: the account is underwater and can be liquidated

Solidity

Comptroller comptroller = Comptroller(0x...);

(uint err, uint liquidity, uint shortfall) = comptroller.getAccountLiquidity(account);
require(err == 0, "liquidity check failed");

if (shortfall > 0) {
    // Account is liquidatable
} else {
    // Account can borrow up to `liquidity` USD worth
}

---

Get Hypothetical Account Liquidity

Calculate what an account's liquidity would be if a hypothetical redeem or borrow were executed. Useful for simulating whether an action would make a position unsafe.

function getHypotheticalAccountLiquidity(
    address account,
    address mTokenModify,
    uint redeemTokens,
    uint borrowAmount
) public view returns (uint, uint, uint)

Parameter	Type	Description
account	address	The account to simulate
mTokenModify	address	The mToken market to hypothetically interact with
redeemTokens	uint	The number of mTokens to hypothetically redeem
borrowAmount	uint	The amount of underlying to hypothetically borrow
returns	(uint, uint, uint)	(error, hypotheticalLiquidity, hypotheticalShortfall)

---

Liquidation Calculate Seize Tokens

Calculate how many collateral mTokens a liquidator would seize for a given repay amount.

function liquidateCalculateSeizeTokens(
    address mTokenBorrowed,
    address mTokenCollateral,
    uint actualRepayAmount
) external view returns (uint, uint)

Parameter	Type	Description
mTokenBorrowed	address	The market in which the borrow is being repaid
mTokenCollateral	address	The market in which collateral will be seized
actualRepayAmount	uint	The amount of underlying being repaid
returns	(uint, uint)	(error, seizeTokens) - the number of collateral mTokens to seize

---

Market Information

Get All Markets

Returns the list of all mToken markets currently listed in the protocol.

function getAllMarkets() public view returns (MToken[] memory)

---

Markets

Query the collateral factor and listing status of a specific market.

function markets(address mToken) external view returns (bool isListed, uint collateralFactorMantissa)

Return	Type	Description
isListed	bool	Whether the market is listed in the Comptroller
collateralFactorMantissa	uint	The collateral factor, scaled by 1e18 (e.g. 0.75e18 = 75%)

---

Close Factor

The maximum percentage of a borrower's debt that can be repaid in a single liquidation.

function closeFactorMantissa() public view returns (uint)

Scaled by 1e18. For example, 0.5e18 means a liquidator can repay up to 50% of the borrow in one transaction.

Typical range: 0.05e18 (5%) to 0.9e18 (90%). Note: the setter performs an admin check only - range validation is not enforced on-chain.

---

Liquidation Incentive

The discount on collateral that liquidators receive, expressed as a multiplier.

function liquidationIncentiveMantissa() public view returns (uint)

Scaled by 1e18. For example, 1.1e18 means liquidators receive a 10% discount on seized collateral.

---

Borrow Caps

function borrowCaps(address mToken) public view returns (uint)

Returns the maximum amount of underlying that can be borrowed from a market. A value of 0 means no cap.

---

Supply Caps

function supplyCaps(address mToken) public view returns (uint)

Returns the maximum amount of underlying that can be supplied to a market. A value of 0 means no cap.

---

Rewards

Claim Reward

Claim accrued WELL rewards. Multiple overloads are available depending on how targeted you want the claim to be.

// Claim all rewards for msg.sender across all markets
function claimReward() public

// Claim all rewards for a specific account
function claimReward(address holder) public

// Claim rewards for a specific account in specific markets
function claimReward(address holder, MToken[] memory mTokens) public

// Claim rewards for multiple accounts, specifying markets and sides
function claimReward(
    address[] memory holders,
    MToken[] memory mTokens,
    bool borrowers,
    bool suppliers
) public

Parameter	Type	Description
holders	address[]	The accounts to claim for
mTokens	MToken[]	The markets to claim from
borrowers	bool	Whether to claim borrow-side rewards
suppliers	bool	Whether to claim supply-side rewards

Solidity

Comptroller comptroller = Comptroller(0x...);

// Simple: claim everything for yourself
comptroller.claimReward();

// Targeted: claim supply-side rewards only, for specific markets
MToken[] memory markets = new MToken[](1);
markets[0] = MToken(mUSDC);
address[] memory holders = new address[](1);
holders[0] = msg.sender;
comptroller.claimReward(holders, markets, false, true);

---

Events

Event	Parameters
MarketListed	MToken mToken
MarketEntered	MToken mToken, address account
MarketExited	MToken mToken, address account
NewCloseFactor	uint oldCloseFactorMantissa, uint newCloseFactorMantissa
NewCollateralFactor	MToken mToken, uint oldCollateralFactorMantissa, uint newCollateralFactorMantissa
NewLiquidationIncentive	uint oldLiquidationIncentiveMantissa, uint newLiquidationIncentiveMantissa
NewPriceOracle	PriceOracle oldPriceOracle, PriceOracle newPriceOracle
NewPauseGuardian	address oldPauseGuardian, address newPauseGuardian
ActionPaused	string action, bool pauseState
ActionPaused	MToken mToken, string action, bool pauseState
NewBorrowCap	MToken indexed mToken, uint newBorrowCap
NewBorrowCapGuardian	address oldBorrowCapGuardian, address newBorrowCapGuardian
NewSupplyCap	MToken indexed mToken, uint newSupplyCap
NewSupplyCapGuardian	address oldSupplyCapGuardian, address newSupplyCapGuardian
NewRewardDistributor	MultiRewardDistributor oldRewardDistributor, MultiRewardDistributor newRewardDistributor

---

Error Codes

All Comptroller functions that return a uint use 0 for success. Non-zero values correspond to:

Code	Name	Description
0	NO_ERROR	Success
1	UNAUTHORIZED	Caller is not authorized
2	COMPTROLLER_MISMATCH	mToken's comptroller does not match
3	INSUFFICIENT_SHORTFALL	Account is not underwater (cannot liquidate)
4	INSUFFICIENT_LIQUIDITY	Not enough liquidity for the operation
5	INVALID_CLOSE_FACTOR	Close factor is outside valid range
6	INVALID_COLLATERAL_FACTOR	Collateral factor exceeds maximum (90%)
7	INVALID_LIQUIDATION_INCENTIVE	Liquidation incentive is invalid
8	MARKET_NOT_ENTERED	Account has not entered this market
9	MARKET_NOT_LISTED	Market is not listed in the Comptroller
10	MARKET_ALREADY_LISTED	Market has already been listed
11	MATH_ERROR	Internal math error
12	NONZERO_BORROW_BALANCE	Cannot exit market with outstanding borrows
13	PRICE_ERROR	Oracle returned an invalid price
14	REJECTION	Comptroller rejected the operation
15	SNAPSHOT_ERROR	Account snapshot failed
16	TOO_MANY_ASSETS	Account has entered too many markets
17	TOO_MUCH_REPAY	Repay amount exceeds allowed close amount

---

Failure Info

The info field in the Failure event provides granular context. These correspond to the ComptrollerErrorReporter.FailureInfo enum:

Code	Name
0	ACCEPT_ADMIN_PENDING_ADMIN_CHECK
1	ACCEPT_PENDING_IMPLEMENTATION_ADDRESS_CHECK
2	EXIT_MARKET_BALANCE_OWED
3	EXIT_MARKET_REJECTION
4	SET_CLOSE_FACTOR_OWNER_CHECK
5	SET_CLOSE_FACTOR_VALIDATION
6	SET_COLLATERAL_FACTOR_OWNER_CHECK
7	SET_COLLATERAL_FACTOR_NO_EXISTS
8	SET_COLLATERAL_FACTOR_VALIDATION
9	SET_COLLATERAL_FACTOR_WITHOUT_PRICE
10	SET_IMPLEMENTATION_OWNER_CHECK
11	SET_LIQUIDATION_INCENTIVE_OWNER_CHECK
12	SET_LIQUIDATION_INCENTIVE_VALIDATION
13	SET_MAX_ASSETS_OWNER_CHECK
14	SET_PENDING_ADMIN_OWNER_CHECK
15	SET_PENDING_IMPLEMENTATION_OWNER_CHECK
16	SET_PRICE_ORACLE_OWNER_CHECK
17	SUPPORT_MARKET_EXISTS
18	SUPPORT_MARKET_OWNER_CHECK
19	SET_PAUSE_GUARDIAN_OWNER_CHECK
20	SET_GAS_AMOUNT_OWNER_CHECK