> ## 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. # AI skills for building on Arc > Use Circle's open source AI skills to accelerate development on Arc with AI-assisted IDEs. Skills give AI coding tools specialized knowledge for building on Arc and with Circle's products, including USDC, agent wallets, crosschain transfers, and smart contracts. Skills are available in the [circlefin/skills](https://github.com/circlefin/skills) repository. ## Installation Install Circle Skills with the command-line. ```shell Claude Code icon="https://mintcdn.com/arcio-docs/DcVxxFlqh75sTiVQ/images/claude-logo.png?fit=max&auto=format&n=DcVxxFlqh75sTiVQ&q=85&s=b0262a5319054feab00173c330431e02" theme={null} /plugin marketplace add circlefin/skills /plugin install circle-skills@circle ``` ```shell Vercel Skills CLI icon="https://mintcdn.com/arcio-docs/DcVxxFlqh75sTiVQ/images/vercel_logo.png?fit=max&auto=format&n=DcVxxFlqh75sTiVQ&q=85&s=9a66052e003d6b18378e0d8a1e0f35f5" theme={null} npx skills add circlefin/skills ``` ## Available skills | Skill | What it covers | | :- | :- | | [`use-arc`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md) | Chain config, contract deployment, viem/wagmi integration, bridging via CCTP | | [`use-circle-cli`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-cli/SKILL.md) | Unified CLI for agent wallets, x402 payments, and crosschain transfers | | [`use-agent-wallet`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-agent-wallet/SKILL.md) | Email/OTP login, wallet creation, status checks, balance inspection | | [`fund-agent-wallet`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/fund-agent-wallet/SKILL.md) | Fund with USDC via fiat on-ramp, crypto transfer, or Gateway deposit | | [`agent-wallet-policy`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/agent-wallet-policy/SKILL.md) | View and reset per-tx, daily, weekly, and monthly USDC spending caps | | [`pay-via-agent-wallet`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/pay-via-agent-wallet/SKILL.md) | Pay paid APIs in USDC via x402 (search, market data, weather, news, sports) | | [`use-usdc`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md) | Balances, transfers, approvals, verification across EVM and Solana | | [`bridge-stablecoin`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md) | CCTP bridging with App Kit, progress tracking, EVM and Solana | | [`swap-tokens`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/swap-tokens/SKILL.md) | Same-chain swaps via App Kit or Swap Kit; combine with bridge for crosschain | | [`use-gateway`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md) | Gateway unified balance for sub-500ms crosschain transfers | | [`unify-balance`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/unify-balance/SKILL.md) | Crosschain USDC balance via App Kit or Unified Balance Kit | | [`use-circle-wallets`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md) | Choose between developer-controlled, user-controlled, and modular wallets | | [`use-developer-controlled-wallets`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md) | Custodial wallets for payouts, treasury, subscriptions, automation | | [`use-user-controlled-wallets`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md) | Embedded wallets with social login or OTP/PIN, no seed phrases | | [`use-modular-wallets`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md) | Passkey auth and gasless transactions; ERC-4337 and ERC-6900 | | [`use-smart-contract-platform`](https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md) | Deploy/import/call/monitor contracts; ERC-20/721/1155 templates |