> ## 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. # Get an x402 transfer by ID > Retrieves a single x402 transfer by its unique identifier. ## OpenAPI ````yaml openapi/gateway-nanopayments.yaml get /v1/x402/transfers/{id} openapi: 3.0.3 info: title: Gateway Nanopayments version: 1.0.0 description: > Gateway Nanopayments settles gasless USDC payments for the x402 protocol using Circle Gateway's batched settlement infrastructure. Sellers verify buyer authorizations and settle net positions in bulk onchain. servers: - url: https://gateway-api-testnet.circle.com - url: https://gateway-api.circle.com security: [] tags: - name: Settlement description: >- Verify buyer-signed x402 authorizations and submit them for batched settlement through Circle Gateway. - name: Batched transfers description: >- Query the batched USDC transfers Gateway settles from accepted x402 authorizations. - name: Supported payment kinds description: Discover the x402 payment schemes and networks this facilitator supports. paths: /v1/x402/transfers/{id}: get: tags: - Batched transfers summary: Get an x402 transfer by ID description: Retrieves a single x402 transfer by its unique identifier. operationId: GetX402TransferById parameters: - in: path name: id required: true schema: type: string format: uuid description: Transfer UUID. responses: '200': description: The transfer content: application/json: schema: $ref: '#/components/schemas/X402TransferResponse' '404': description: Transfer not found components: schemas: X402TransferResponse: type: object description: Response containing details of an x402 transfer. properties: id: type: string format: uuid description: Unique identifier for the transfer. status: type: string enum: - received - batched - confirmed - completed - failed description: | Current status of the x402 transfer: - `received`: Transfer has been submitted and accepted - `batched`: Transfer has been included in a batch for processing - `confirmed`: Transfer has been confirmed onchain - `completed`: Transfer is fully complete - `failed`: Transfer has failed token: type: string description: Token symbol (e.g., USDC). example: USDC sendingNetwork: type: string description: CAIP-2 network identifier for the sending chain. example: eip155:11155111 recipientNetwork: type: string description: CAIP-2 network identifier for the recipient chain. example: eip155:11155111 fromAddress: type: string description: Sender address. toAddress: type: string description: Recipient address. amount: type: string description: Transfer amount in atomic units. nonce: type: string description: EIP-3009 nonce. txHash: type: string nullable: true description: >- Batch-level settlement transaction hash, shared by all transfers in the same batch. Remains null until included in a batch with a settlement transaction hash. createdAt: type: string format: date-time description: Timestamp when the transfer was created. updatedAt: type: string format: date-time description: Timestamp when the transfer was last updated. required: - id - status - token - sendingNetwork - recipientNetwork - fromAddress - toAddress - amount - nonce - txHash - createdAt - updatedAt ````