> ## Documentation Index > Fetch the complete documentation index at: https://developers.circle.com/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. 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. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}. > Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts. > Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md. > Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md. > Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers. > Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews. > Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming. > Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md. > Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors. > API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product. > Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes. > When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records. > Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md. # Gas Station contract addresses ## EVM chains Built with ERC-4337 compatible smart contracts, Gas Station for Circle Wallets allows developers to sponsor network fees for SCA wallet users. If a transaction meets the policies you set, Gas Station calls these contracts to cover the network fee. The following are the smart contract addresses that power Gas Station on EVM blockchains: | Blockchain | Network | Blockchain Address | | :- | :- | :- | | Arbitrum | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://arbiscan.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Arbitrum | Sepolia Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://sepolia.arbiscan.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Arc | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://explorer.arc.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Arc | Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://explorer.testnet.arc.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Avalanche | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://snowtrace.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Avalanche | Fuji Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://testnet.snowtrace.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Base | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://basescan.org/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Base | Sepolia Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://base-sepolia.blockscout.com/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Ethereum | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://etherscan.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Ethereum | Sepolia Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://sepolia.etherscan.io/address/0x7cea357b5ac0639f89f9e378a1f03aa5005c0a25) | | Monad | Monad Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://monadvision.com/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Monad | Monad Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://testnet.monadexplorer.com/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Optimism | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://optimistic.etherscan.io/address/0x7cea357b5ac0639f89f9e378a1f03aa5005c0a25) | | Optimism | Sepolia Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://sepolia-optimism.etherscan.io/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Polygon | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://polygonscan.com/address/0x7cea357b5ac0639f89f9e378a1f03aa5005c0a25) | | Polygon | Amoy Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://amoy.polygonscan.com/address/0x7cea357b5ac0639f89f9e378a1f03aa5005c0a25) | | Unichain | Mainnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://uniscan.xyz/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | | Unichain | Sepolia Testnet | [`0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25`](https://unichain-sepolia.blockscout.com/address/0x7ceA357B5AC0639F89F9e378a1f03Aa5005C0a25) | ## Non-EVM chains | Blockchain | Network | Blockchain Address | | :- | :- | :- | | Solana | Mainnet | • [`9kHTT3RgH51FhMzKjxk8XXHoNnVjEjK5JnwTVSP8rXTy`](https://solscan.io/account/9kHTT3RgH51FhMzKjxk8XXHoNnVjEjK5JnwTVSP8rXTy?cluster=mainnet)
• [`HcSvhXR7yNdNmnz8QjWbo9EnWm9zB4nfX6MoJAXfEdBa`](https://solscan.io/account/HcSvhXR7yNdNmnz8QjWbo9EnWm9zB4nfX6MoJAXfEdBa?cluster=mainnet)
• [`6nvUkyJG5j6rH3Hfm15mJNgPMJ1cxHQapfm5K3k647iv`](https://solscan.io/account/6nvUkyJG5j6rH3Hfm15mJNgPMJ1cxHQapfm5K3k647iv?cluster=mainnet)
• [`FU8KibWzoNfnsytAfc3fRG8AZMMB4hS7Pfx9NyNSXt1D`](https://solscan.io/account/FU8KibWzoNfnsytAfc3fRG8AZMMB4hS7Pfx9NyNSXt1D?cluster=mainnet)
• [`HCcQZ3UPYR1XQSzMvLUH8yVuZKaxi5J5n7mHkccMW7D9`](https://solscan.io/account/HCcQZ3UPYR1XQSzMvLUH8yVuZKaxi5J5n7mHkccMW7D9?cluster=mainnet) | | Solana | Devnet | • [`99TfgApJDd6WSpVq5wBhbwqieoFYs4buzv8p9Uv5monw`](https://solscan.io/account/99TfgApJDd6WSpVq5wBhbwqieoFYs4buzv8p9Uv5monw?cluster=devnet)
• [`8XejFT3EpdFfxgPimne75us4wdnctSznu9Jvx3wLhJkd`](https://solscan.io/account/8XejFT3EpdFfxgPimne75us4wdnctSznu9Jvx3wLhJkd?cluster=devnet)
• [`BS5QyQcsFbrep8mNrCh5DtnTaihB2C2HUZEW8UJbY2xM`](https://solscan.io/account/BS5QyQcsFbrep8mNrCh5DtnTaihB2C2HUZEW8UJbY2xM?cluster=devnet)
• [`2AMHVbmq5oz8zUibEw3KSPR8btJKqB1jbp1azepprt7E`](https://solscan.io/account/2AMHVbmq5oz8zUibEw3KSPR8btJKqB1jbp1azepprt7E?cluster=devnet)
• [`PKWh66GhWw5HQW2dDo9LvbuNd6b4EbJ49NmCi1Dsu3A`](https://solscan.io/account/PKWh66GhWw5HQW2dDo9LvbuNd6b4EbJ49NmCi1Dsu3A?cluster=devnet) | | Aptos | Mainnet | • [`0xea9434b70c638db3a8175dd9b4db66e1b6ad03b9e4de01a67488b4a2e93b23cd`](https://explorer.aptoslabs.com/account/0xea9434b70c638db3a8175dd9b4db66e1b6ad03b9e4de01a67488b4a2e93b23cd?network=mainnet)
• [`0x1e3c8ad3abedab489849b3c294ec3ab1755279d2c6ec7ae3c1955dc1e07769d6`](https://explorer.aptoslabs.com/account/0x1e3c8ad3abedab489849b3c294ec3ab1755279d2c6ec7ae3c1955dc1e07769d6?network=mainnet)
• [`0x1e0b80ef6e26a3440a87f26aec0975ae7aec27c65dd6c8622bda7c9f2dc74c6e`](https://explorer.aptoslabs.com/account/0x1e0b80ef6e26a3440a87f26aec0975ae7aec27c65dd6c8622bda7c9f2dc74c6e?network=mainnet)
• [`0x4548236f98f7ceb227b452dee8e5ff1f6db2ac48d54b22ce7ae2eafa88ec26a1`](https://explorer.aptoslabs.com/account/0x4548236f98f7ceb227b452dee8e5ff1f6db2ac48d54b22ce7ae2eafa88ec26a1?network=mainnet)
• [`0x0b18439154c6a7007343b0198eca7aef1874f537589ad47d16b74ee3a27fe882`](https://explorer.aptoslabs.com/account/0x0b18439154c6a7007343b0198eca7aef1874f537589ad47d16b74ee3a27fe882?network=mainnet) | | Aptos | Testnet | • [`0xc00c6f9cd50104a09190209ad4edd371453fe6f6294d0af306c94eae74ed7fe5`](https://explorer.aptoslabs.com/account/0xc00c6f9cd50104a09190209ad4edd371453fe6f6294d0af306c94eae74ed7fe5?network=testnet)
• [`0x8bed386d4a4a950ad486e277c43cbd273b5304b3dfa12b0b00f6dad555578d18`](https://explorer.aptoslabs.com/account/0x8bed386d4a4a950ad486e277c43cbd273b5304b3dfa12b0b00f6dad555578d18?network=testnet)
• [`0xbb97626c7968b94a6a53c972891f1ee342364e1dcc32118c14c60b0d74629d5a`](https://explorer.aptoslabs.com/account/0xbb97626c7968b94a6a53c972891f1ee342364e1dcc32118c14c60b0d74629d5a?network=testnet)
• [`0x7fc660c2b729b1f4c7464a865f3819f01e4ad1cfa4f1fe774598f6dc2fc97e69`](https://explorer.aptoslabs.com/account/0x7fc660c2b729b1f4c7464a865f3819f01e4ad1cfa4f1fe774598f6dc2fc97e69?network=testnet)
• [`0x5e3517733659e3a8a544aa81605a5c687df879b6fb5f0b34594b3635f59edbf3`](https://explorer.aptoslabs.com/account/0x5e3517733659e3a8a544aa81605a5c687df879b6fb5f0b34594b3635f59edbf3?network=testnet) | **Solana** Gas Station on Solana is powered by fee-payers: programs that cover network fees for users on your behalf. If a transaction meets the policies you set, Gas Station calls the fee payer to sponsor the network fee of the transaction. Gas Station is available on both mainnet and devnet.