> ## Documentation Index > Fetch the complete documentation index at: https://docs.arc.io/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Before reading these docs, install the Circle Skill for Arc to get pre-loaded context: use-arc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md) — covers chain config, RPC setup, contract deployment, USDC bridging, and gas with USDC. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills. > USDC is the gas token. Arc uses USDC for gas fees, not ETH. Configure gas payment in USDC when submitting transactions. > Read EVM differences before writing Arc code. Arc targets the Osaka EVM baseline. Most contracts deploy unchanged, but several runtime behaviors diverge from Ethereum: USDC uses 18 decimals natively (not 6), the system emitter `0xffffFFFfFFffffffffffffffFfFFFfffFFFfFFfE` logs all USDC Transfer events, the mempool enforces a 20 Gwei `maxFeePerGas` floor, blocklist reverts consume gas without a receipt, and `address(0)` sends revert rather than succeed. https://docs.arc.io/arc/references/evm-differences.md is the canonical reference for all Arc-specific runtime behaviors. Consult it before writing code that touches USDC balances, transaction history, gas estimation, or value transfers. > Sub-second finality. Transactions are final in under 1 second. No need to wait for multiple block confirmations. > Use App Kits for multichain payment and liquidity capabilities. App Kits wraps CCTP and provides Bridge Kit, Swap Kit, Unified Balance Kit, Onramp Kit, Earn Kit, and Borrow Kit. Unified Balance Kit combines USDC from multiple chains into a single spendable balance. Earn Kit integrates earn opportunities into your app. Borrow Kit lets users borrow USDC against cirBTC collateral on Arc. > Use Arc Foundry for contract development. Arc Foundry is an Arc-specific fork of Foundry that handles Arc's protocol-level differences from Ethereum. It provides arc-forge, arc-cast, and arc-anvil. Install it before deploying contracts: https://docs.arc.io/arc/tutorials/install-arc-foundry.md. > Arc is available on both Testnet and Mainnet. See https://docs.arc.io/arc/references/connect-to-arc.md for RPC endpoints and https://faucet.circle.com for testnet tokens. > Always check Contract Addresses: https://docs.arc.io/arc/references/contract-addresses.md > Building beyond Arc? Circle offers skills for the full platform: use-usdc (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md), use-circle-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md), use-developer-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md), use-user-controlled-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md), use-modular-wallets (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md), use-gateway (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md), use-smart-contract-platform (https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md). Full Circle developer docs: https://developers.circle.com/llms.txt. # Oracles > Oracle providers for bringing external market data and offchain signals into Arc smart contracts. Connect your Arc smart contracts to real-world data using the oracle providers listed below. They offer price feeds and related infrastructure for DeFi, trading, lending, and other financial applications. If your application also needs to query historical onchain data, see [Data indexers](/arc/tools/data-indexers). ## Providers ### [Chainlink](https://chain.link) Decentralized oracle network for bringing market data and other offchain information onchain. Chainlink Data Feeds aggregate multiple data sources and publish secure, widely used feeds for lending, trading, stablecoins, and tokenized assets. * [**Data Feeds**](https://docs.chain.link/data-feeds): Access decentralized price feeds for smart contract integrations. * [**Data Streams**](https://docs.chain.link/data-streams): Retrieve low-latency market data delivered through a pull-based model. * [**Feed Explorer**](https://data.chain.link): Browse available feeds and contract addresses across supported networks. * [**Contract Addresses**](https://docs.chain.link/data-feeds/price-feeds/addresses): Find deployed price feed contract addresses across supported networks. ### [Chronicle](https://chroniclelabs.org) Onchain data infrastructure for high-integrity price feeds and tokenized asset verification. Chronicle originated as the oracle for Sky (MakerDAO) and provides DeFi price feeds alongside proof-of-asset attestations for lending, stablecoins, tokenized treasuries, and other RWAs. * [**DeFi Price Feeds**](https://chroniclelabs.org/dashboard/oracles): Access high-integrity feeds purpose-built for lending, stablecoins, and other onchain financial applications. * [**Proof of Asset**](https://chroniclelabs.org/dashboard/proofofasset): Provide cryptographic attestations of reserves and collateral for tokenized treasuries, stablecoins, RWAs, and other assets where verifiable backing is essential. * [**Docs**](https://docs.chroniclelabs.org/): Get started with Chronicle's oracle integration guides. ### [Pyth](https://www.pyth.network) Real-time, first-party market data oracle for onchain applications. Pyth provides price feeds across crypto, equities, FX, metals, and more, with pull and push delivery models for different latency and cost requirements. * [**Price Feeds**](https://docs.pyth.network/price-feeds): Integrate real-time price data into Arc smart contracts. * [**EVM Contract Addresses**](https://docs.pyth.network/price-feeds/core/contract-addresses/evm): Find deployed contract addresses for EVM-compatible chains. ### [RedStone](https://www.redstone.finance) Modular oracle network for secure, real-time price feeds and specialized market data. RedStone supports push, pull, and hybrid delivery models, with coverage across crypto assets, LSTs, LRTs, RWAs, tokenized funds, FX, and other custom data feeds for DeFi and institutional applications. * [**Docs**](https://docs.redstone.finance/docs/introduction/): Learn about RedStone's oracle architecture and supported integration models. * [**Pull Model**](https://docs.redstone.finance/docs/dapps/redstone-pull/): Inject signed oracle data directly into user transactions for low-latency, gas-efficient integrations. * [**Push Feeds**](https://app.redstone.finance/push-feeds): View deployed push feed contract addresses. * [**Pull Feeds**](https://app.redstone.finance/pull-feeds): Browse available pull feed configurations and supported assets. * [**Price Feeds**](https://www.redstone.finance/price-feeds): Browse RedStone's supported asset coverage and feed types. ### [Stork](https://www.stork.network) Ultra-low-latency oracle protocol for real-time market data. Stork provides fast, pull-based delivery with cryptographic verifiability for DeFi applications that require sub-second pricing. * [**Docs**](https://docs.stork.network/): Get started with Stork's oracle integration guides. * [**EVM Contract Addresses**](https://docs.stork.network/resources/contract-addresses/evm#arc): Find Stork's deployed contracts on Arc.