> ## 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. # Match funding model > How burn-side and mint-side participants prefund their Match activity, and what happens to balances before, during, and after a fill. Match is a two-sided market: burn-side participants destroy USDC and receive USD, while mint-side participants deposit USD and receive USDC. Each side funds its activity differently, carries a different fee direction, and follows a different exit path. Understanding how each side funds activity, particularly the restricted nature of mint-side balances, is essential before placing orders. ## Burn side Burn-side participants hold USDC in their existing Circle Mint wallet. No separate funding step is required. When you place a burn-side order, Circle reserves the order amount from your Circle Mint wallet balance. The reserved amount is no longer available for new orders or withdrawals until the auction clears. * **If the order fills:** You pay the clearing fee (deducted from the filled amount in basis points), and receive USD settlement to your linked fiat account. * **If the order is unfilled or cancelled:** The reserved USDC is released back to your available balance. Burn-side USDC is standard Circle Mint USDC. It is withdrawable to blockchain addresses at any time when not reserved by a resting order. ## Mint side Mint-side participants fund their activity by wiring USD to their Match fiat account. This account is separate from the standard Circle Mint wallet. Once the inbound wire settles, Circle automatically converts the USD into Match-only USDC. This balance is segregated from your standard Circle Mint wallet and does not appear there. After a USD wire settles, you hold Match-only USDC, not fiat. This balance is not fiat sitting idle. It is USDC, held in a restricted, Match-only construct. It cannot be sent to blockchain addresses and does not appear in your standard Circle Mint wallet. * **If the order fills:** You receive USDC in your standard Circle Mint wallet (not in the restricted balance) and earn the clearing fee as a rebate added to the received amount. Post-fill USDC in the standard Mint wallet is withdrawable normally. * **If the order is unfilled or cancelled:** The restricted USDC balance remains in the Match account until you submit a withdrawal request or place a new order. ### Exit path for restricted USDC The only way to exit a restricted Match-only USDC balance is to submit a withdrawal request. Circle burns the restricted USDC and wires the equivalent USD to your linked fiat account. This withdrawal is fee-free: no standard Circle Mint burn fee applies. There is no blockchain exit for restricted USDC. ## Burn side vs. mint side comparison | | Burn side | Mint side | | - | - | - | | **Prefund type** | USDC in existing Circle Mint wallet | USD wire to Match fiat account, converted to restricted USDC on settlement | | **Fee direction** | Pays the clearing fee | Receives the clearing fee as a rebate | | **Post-fill currency received** | USD (to linked fiat account) | USDC (to standard Circle Mint wallet) | | **Exit path (unfilled balance)** | USDC releases to standard Mint wallet; withdrawable to blockchain | No-fee USD wire to linked fiat account only; no blockchain exit | ## Balance fields Your Match account summary exposes three balance fields for the mint-side restricted USDC: * `total`: your full Match USDC balance. * `reserved`: the portion held by open resting orders, not available for new orders. * `available`: `total` minus `reserved` (what you can use for new orders). The account summary is a best-effort snapshot. Activity figures may lead settlement; for exact reconciliation, rely on order and settlement records rather than the summary alone. ## Order size constraints All orders (burn side and mint side) must be a minimum of $100 and a multiple of $100. This granularity is required for integer-cent fee arithmetic at basis-point precision during clearing.