> For the complete documentation index, see [llms.txt](https://andrecronje.gitbook.io/yearn-finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://andrecronje.gitbook.io/yearn-finance/developers/misc-resources/smart-contract-integration/itoken.md).

# itoken

| Contract | ABI                                                                                     | Address                                                                                        |
| -------- | --------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| iEther   | [JSON](https://github.com/iearn-finance/itoken/blob/master/build/contracts/IEther.json) | [ieth.iearn.eth](https://etherscan.io/address/0x9dde7cdd09dbed542fc422d18d89a589fa9fd4c0#code) |

## iToken Interface

{% tabs %}
{% tab title="IIEther.sol" %}

```javascript
// Solidity Interface

interface IIEther {
  // Invest ETH
  function invest() external payable;
  function calcPoolValueInETH() external view returns (uint);
  function getPricePerFullShare() external view returns (uint);
  // Redeem any invested tokens from the pool
  function redeem(uint256 _shares) external;
}
```

{% endtab %}
{% endtabs %}

## ERC20 Token Interface

{% tabs %}
{% tab title="TokenInterface.sol" %}

```javascript
// https://theethereum.wiki/w/index.php/ERC20_Token_Standard
contract ERC20Interface {
    function totalSupply() public view returns (uint);
    function balanceOf(address tokenOwner) public view returns (uint balance);
    function allowance(address tokenOwner, address spender) public view returns (uint remaining);
    function transfer(address to, uint tokens) public returns (bool success);
    function approve(address spender, uint tokens) public returns (bool success);
    function transferFrom(address from, address to, uint tokens) public returns (bool success);
    // optional
    function name() external view returns (string);
    function symbol() external view returns (string);
    function decimals() external view returns (string);

    event Transfer(address indexed from, address indexed to, uint tokens);
    event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
}
```

{% endtab %}
{% endtabs %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://andrecronje.gitbook.io/yearn-finance/developers/misc-resources/smart-contract-integration/itoken.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.