API3

API3 is a decentralized oracle network that provides real-time data feeds to smart contracts. Unlike traditional oracles that rely on third-party intermediaries, API3 connects APIs directly to the blockchain through first-party oracles operated by the API providers themselves. This approach reduces trust assumptions and potential points of failure.

What You’ll Be Doing in This Guide

In this tutorial, you’ll learn how to:

1. Integrate API3’s data feeds into your smart contract on the SEI network
2. Retrieve real-time SEI token price data using API3’s proxy contract
3. Understand the structure of API3’s reader proxy interface
4. Deploy and test your integration on SEI

By the end of this guide, you’ll have a working smart contract that can fetch SEI price data from API3’s decentralized oracle network.

Prerequisites

Before starting this tutorial, ensure you have:

Technical Requirements

• Solidity Knowledge: Basic understanding of Solidity smart contract development
• Development Environment: Remix IDE, Hardhat, or similar Solidity development setup
• SEI Network Access: RPC endpoint and mainnet access for SEI

Required Dependencies

• OpenZeppelin Contracts library (@openzeppelin/contracts)
• API3 Contracts library (@api3/contracts)

Install

# npm
npm install @openzeppelin/contracts @api3/contracts
 
# yarn
yarn add @openzeppelin/contracts @api3/contracts
 
# pnpm
pnpm add @openzeppelin/contracts @api3/contracts

SEI Network Configuration

Make sure your development environment is configured for SEI:

• Mainnet RPC: https://evm-rpc.sei-apis.com
• Chain ID: 1329 (mainnet)

Contract Code

Here’s the complete smart contract code for integrating with API3 to read SEI price data:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
 
import "@openzeppelin/contracts/access/Ownable.sol";
import "@api3/contracts/interfaces/IApi3ReaderProxy.sol";
 
contract DataFeedReaderExample is Ownable {
    // This contract reads from a single proxy. Your contract can read from
    // multiple proxies.
    address public proxy;
 
    constructor(address proxy_) Ownable(msg.sender) {
        setProxy(proxy_);
 
    }
 
    // Updating the proxy address is a security-critical action. In this
    // example, only the owner is allowed to do so.
    // You may want to update your proxy to switch to another data feed, enable
    // OEV support, or even switch to another oracle solution. Implementing a
    // method to update proxies is highly recommended.
    function setProxy(address proxy_) public onlyOwner {
        proxy = proxy_;
    }
 
    function readDataFeed()
        external
        view
        returns (int224 value, uint256 timestamp)
    {
        (value, timestamp) = IApi3ReaderProxy(proxy).read();
        // If you have any assumptions about `value` and `timestamp`, make sure
        // to validate them right after reading from the proxy. For example,
        // if the value you are reading is the spot price of an asset, you may
        // want to reject non-positive values...
        require(value > 0, "Value not positive");
        // ...and if the data feed is being updated with a one day-heartbeat
        // interval, you may want to check for that.
        require(
            timestamp + 1 days > block.timestamp,
            "Timestamp older than one day"
        );
        // After validation, you can implement your contract logic here.
 
        // Refer to https://docs.api3.org/dapps/integration/contract-integration.html
        // for more information about how to integrate your contract securely.
    }
}

Contract Breakdown

Key Components:

1. Proxy Address: The contract stores the API3 proxy address that provides SEI price data
2. Data Validation: The contract validates that price values are positive and timestamps are recent
3. IApi3ReaderProxy Interface: This interface provides the read() function to fetch price data

The readDataFeed() Function:

• Returns int224 value: The SEI price (likely in USD with 18 decimal places)
• Returns uint256 timestamp: When the price was last updated
• Validates data freshness (within 1 day)
• Ensures price is positive

Proxy Address

For this tutorial, we’ll be using the following API3 proxy address on SEI:

0x09c6e594DE2EB633902f00B87A43b27F80a31a60

This proxy provides real-time SEI/USD  price data from API3’s decentralized oracle network.

How to Test

1. Deploy the Contract

Using Remix IDE:

1. Open Remix IDE 
2. Create a new file called DataFeedReaderExample.sol
3. Paste the contract code above
4. Compile the contract using Solidity compiler ^0.8.0
5. Deploy with constructor parameter: 0x09c6e594DE2EB633902f00B87A43b27F80a31a60

Using Hardhat:

const proxy = '0x09c6e594DE2EB633902f00B87A43b27F80a31a60';
const DataFeedReader = await ethers.getContractFactory('DataFeedReaderExample');
const reader = await DataFeedReader.deploy(proxy);
await reader.deployed();

2. Read Price Data

After deployment, call the readDataFeed() function to retrieve the current SEI price:

// Using ethers.js
const result = await reader.readDataFeed();
console.log('SEI Price:', ethers.utils.formatUnits(result.value, 18));
console.log('Last Updated:', new Date(result.timestamp * 1000));

Expected Output Format:

• value: SEI price in USD (with 18 decimals, e.g., 3000000000000000 = $0.3)
• timestamp: Unix timestamp of the last price update

3. Integration Examples

Basic Price Display:

function getSEIPriceFormatted() external view returns (string memory) {
    (int224 value, uint256 timestamp) = readDataFeed();
    return string(abi.encodePacked("$", uint224(value) / 1e18));
}