> ## 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. # Supported payment rails > Reference for the fiat payment rails Circle Mint supports—Fedwire, SWIFT, RTP, SEPA, SPEI, CHATS, PIX, CUBIX, and book transfers—including currencies, regions, settlement timing, and API endpoints. Circle Mint supports a range of fiat payment rails for funding deposits and sending payouts. Use this reference to decide how a counterparty should fund a deposit or receive a payout based on currency, region, and the settlement speed you need. Circle auto-routes deposits and payouts submitted to `/v1/businessAccount/banks/wires` to the appropriate rail based on the linked bank's capabilities, while PIX and CUBIX have dedicated endpoints. Every rail below supports both deposits and payouts. ## Rail comparison | Rail | Currencies | Region | Settlement time | API endpoint | | - | - | - | - | - | | Fedwire | USD | United States (domestic) | 1–3 business days; same business day if before daily cutoff | `/v1/businessAccount/banks/wires` | | SWIFT | USD, EUR | Cross-border | 1–3 business days; longer with intermediary banks | `/v1/businessAccount/banks/wires` | | RTP | USD | United States (domestic) | Near-instant, 24/7 | `/v1/businessAccount/banks/wires` | | SEPA | EUR | SEPA zone (domestic) | Same or next business day | `/v1/businessAccount/banks/wires` | | SEPA Instant | EUR | SEPA zone (domestic) | Near-instant, 24/7 | `/v1/businessAccount/banks/wires` | | SPEI | MXN | Mexico (domestic) | Near-instant | `/v1/businessAccount/banks/wires` | | CHATS | HKD | Hong Kong (domestic) | Under 5 minutes | `/v1/businessAccount/banks/wires` | | Book transfer | USD, EUR | Domestic same-bank | Near-instant, banking hours | `/v1/businessAccount/banks/wires` | | PIX | BRL | Brazil (domestic) | Near-instant, 24/7 | `/v1/businessAccount/banks/pix` | | CUBIX | USD | Contact Circle | Contact Circle | `/v1/businessAccount/banks/cubix` | ## USD rails ### Fedwire Fedwire is the domestic US wire rail that runs over the Federal Reserve's wholesale wire system. Wires settle same business day when submitted before the daily Fedwire cutoff; otherwise they settle the next business day. The linked bank must have a US ABA routing number. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts. ### SWIFT SWIFT is the international wire rail and supports both USD and EUR. The linked bank must have a SWIFT/BIC, and for accounts in SEPA-zone countries an IBAN is also required. Settlement typically takes 1–3 business days but can take longer when intermediary banks are involved. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts. ### RTP RTP is the Real-Time Payments network in the United States. It is domestic-only and settles near-instantly, 24/7. There is no separate endpoint: Circle auto-routes deposits and payouts submitted to `/v1/businessAccount/banks/wires` over RTP when the linked US bank participates in the network. Per-rail transaction limits are subject to Circle's banking partner configuration; contact Circle to confirm the limit. ### CUBIX CUBIX is a USD rail exposed through a dedicated endpoint, `/v1/businessAccount/banks/cubix`. Use this endpoint to link a CUBIX-capable account and to submit deposits and payouts. Contact Circle to confirm the geographic scope, settlement timing, and account prerequisites for CUBIX before integrating. ### Book transfer When the linked bank account and a Circle account are held at the same banking partner, Mint can route deposits and payouts as a book-to-book transfer in that bank. These transfers are typically near-instant during banking hours and support USD and EUR. There is no separate endpoint: Mint chooses this path automatically when the linked bank matches. ## EUR rails ### SEPA SEPA is the Single Euro Payments Area credit transfer rail for accounts in SEPA-zone countries. Settlement is same or next business day. The linked bank must be in a SEPA country and provide an IBAN. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts. ### SEPA Instant SEPA Instant settles near-instantly, 24/7, subject to the linked bank's participation in the SEPA Instant scheme. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts; Circle auto-routes through SEPA Instant when the linked bank supports it. Per-rail transaction limits are subject to scheme and banking partner configuration; contact Circle to confirm the limit. ## MXN rails ### SPEI SPEI (Sistema de Pagos Electrónicos Interbancarios) is Mexico's domestic real-time payment system. Settlement is near-instant. The linked bank must be configured for SPEI. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts. ## HKD rails ### CHATS CHATS (Clearing House Automated Transfer System) is Hong Kong's real-time gross settlement system. Settlement is under 5 minutes. The linked bank must participate in CHATS. Use `/v1/businessAccount/banks/wires` to link the account and to submit payouts. Per-rail transaction limits are subject to scheme and banking partner configuration; contact Circle to confirm the limit. ## BRL rails ### PIX PIX is Brazil's instant payment system, operated by the Banco Central do Brasil. Settlement is near-instant, 24/7. The linked Brazil bank must be enrolled for PIX. PIX uses a dedicated endpoint surface: `/v1/businessAccount/banks/pix` to link an account and to submit payouts, and `/v1/businessAccount/banks/pix/{id}/instructions` to retrieve deposit instructions for a linked PIX account. Once fiat is received and credited to your Circle Mint account, Circle typically completes onchain minting in 15 minutes. For the full lifecycle from fiat receipt to onchain credit, see [How minting works](/circle-mint/concepts/how-minting-works).