# Contract Interfaces

This section documents the public and external functions of SIR Protocol's core contracts. It is intended for developers building on top of the protocol — bots, aggregators, frontends, and other integrations.

For deployed contract addresses, see [Deployments](/protocol-overview/deployments.md).

{% hint style="info" %}
The core contracts are deployed on **Ethereum**, **HyperEVM**, and **MegaETH**. Function signatures are nearly identical across chains, but there are meaningful differences noted on each page. Always verify against the deployment you are targeting.
{% endhint %}

## Contract Pages

| Contract                                                                         | Description                                                         |
| -------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
| [Vault](/protocol-overview/smart-contract-interfaces/vault.md)                   | Main entry point for minting and burning APE/TEA tokens             |
| [SIR & Staking](/protocol-overview/smart-contract-interfaces/sir-and-staking.md) | SIR token, staking for dividends, reward claiming, and fee auctions |
| [Price Oracle](/protocol-overview/smart-contract-interfaces/oracle.md)           | TWAP price feed interface                                           |
| [TEA & APE Tokens](/protocol-overview/smart-contract-interfaces/tea-and-ape.md)  | LP token (ERC1155) and leveraged token (ERC20) interfaces           |

## Key Structs

These structs appear throughout the contract interfaces.

### `VaultParameters`

Identifies a specific vault. Used as input to most Vault functions.

```solidity
struct VaultParameters {
    address debtToken;
    address collateralToken;
    int8 leverageTier;       // Range: -2 to +2
}
```

### `Reserves`

Collateral reserves held by a vault, returned by `getReserves()`.

```solidity
struct Reserves {
    uint144 reserveApes;     // Collateral belonging to APE holders
    uint144 reserveLPers;    // Collateral belonging to TEA holders (LPs)
    int64 tickPriceX42;      // Current price in Q21.42 fixed point
}
```

### `VaultState`

On-chain storage representation of a vault's state.

```solidity
struct VaultState {
    uint144 reserve;          // Total reserve (reserveApes + reserveLPers)
    int64 tickPriceSatX42;    // Saturation price in Q21.42 fixed point
    uint48 vaultId;           // Unique vault identifier
}
```

### `Fees`

Fee breakdown returned during mint/burn operations.

```solidity
struct Fees {
    uint144 collateralInOrWithdrawn;   // Net collateral deposited or withdrawn
    uint144 collateralFeeToStakers;    // Fee portion sent to SIR stakers
    uint144 collateralFeeToLPers;      // Fee portion sent to LPers / POL
}
```

### `Auction`

State of a fee auction.

```solidity
struct Auction {
    address bidder;    // Current highest bidder
    uint96 bid;        // Current highest bid amount
    uint40 startTime;  // Auction start timestamp
}
```


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