> ## 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. # Create a crypto payment refund address > Creates a refund address-book entry that can be used as `destination.addressBookId` when refunding a crypto payment intent. This endpoint is used for Circle Singapore (`CIRCLE_SG`) refund flow 2, where the refund goes to a different address while reusing the original payment's Travel Rule originator PII. Provide the original `paymentId` and a hosted VASP in `ownership.custody.vaspId`; the supplied VASP ID must match the VASP associated with the original payment sender. Do not provide recipient `identity` in the request. Identity is derived from the original payment's Travel Rule originator PII. ## OpenAPI ````yaml openapi/payments.yaml post /v1/payments/refundAddresses openapi: 3.0.2 info: version: ${version} title: Crypto Deposits API description: > The Circle Payments API allows you to take payments from your end users via traditional methods such as debit & credit cards and receive settlement in USDC. The Circle Payments API has been designed with any business or internet commerce in mind, not just crypto applications, and it's based on Circle's extensive experience processing millions of card payments since 2014. servers: - url: https://api-sandbox.circle.com - url: https://api.circle.com security: [] tags: - name: Payments description: Create, cancel, refund, and get updates on card payments. - name: Crypto Payment Intents description: Create and track intent for end user to pay via crypto. - name: Crypto Payment Customers description: >- Create and manage Travel Rule customers and customer wallets for crypto payment attribution. - name: Crypto Payment Refund Addresses description: Create refund address-book entries for crypto payment refunds. paths: /v1/payments/refundAddresses: post: tags: - Crypto Payment Refund Addresses summary: Create a crypto payment refund address description: > Creates a refund address-book entry that can be used as `destination.addressBookId` when refunding a crypto payment intent. This endpoint is used for Circle Singapore (`CIRCLE_SG`) refund flow 2, where the refund goes to a different address while reusing the original payment's Travel Rule originator PII. Provide the original `paymentId` and a hosted VASP in `ownership.custody.vaspId`; the supplied VASP ID must match the VASP associated with the original payment sender. Do not provide recipient `identity` in the request. Identity is derived from the original payment's Travel Rule originator PII. operationId: createPaymentRefundAddress requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PaymentRefundAddressCreationRequest' responses: '201': description: >- Refund address successfully created, or original address replayed for a reused idempotency key. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: title: CreatePaymentRefundAddressResponse properties: data: $ref: '#/components/schemas/PaymentRefundAddress' examples: refundAddress: value: data: id: 7418ddb1-1bbf-5506-88f9-209a25c63b8b chain: ETH address: '0x57414adbBbc4BBA36f1dE26b2dc1648b28ae7799' metadata: nickname: Refund recipient identity: type: individual firstName: John lastName: Doe ownership: type: third_party custody: type: hosted vaspId: 581b9b20-28e1-464d-a257-e408733d0857 status: pending createDate: '2026-06-30T12:00:00Z' updateDate: '2026-06-30T12:00:00Z' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/NotAuthorized' '403': $ref: '#/components/responses/Forbidden' '500': $ref: '#/components/responses/InternalServerError' security: - bearerAuth: [] components: schemas: PaymentRefundAddressCreationRequest: type: object required: - idempotencyKey - chain - address - metadata - ownership - paymentId properties: idempotencyKey: $ref: '#/components/schemas/IdempotencyKey' clientEntityId: type: string format: uuid description: >- Optional child entity that should own the refund address. When omitted, the address is PSP-owned/shared. example: 7c1fb25a-f814-4c57-b06f-d5a25bfbf935 paymentId: type: string format: uuid description: >- Original payment identifier. Recipient identity is derived from this payment's Travel Rule originator PII. example: 74fe686b-9142-43ab-9ba9-2e0c9b366d70 chain: $ref: '#/components/schemas/Chain' address: $ref: '#/components/schemas/Address' addressTag: $ref: '#/components/schemas/AddressTag' metadata: $ref: '#/components/schemas/PaymentRefundAddressMetadata' ownership: $ref: '#/components/schemas/PaymentRefundAddressOwnership' description: >- Refund address ownership. `ownership.custody.vaspId` is required and must match the VASP recorded on the original payment. PaymentRefundAddress: type: object description: Refund address-book entry used as a crypto refund destination. properties: clientEntityId: type: string format: uuid description: Child entity that owns the refund address, when applicable. example: 7c1fb25a-f814-4c57-b06f-d5a25bfbf935 id: $ref: '#/components/schemas/Id' chain: $ref: '#/components/schemas/Chain' address: $ref: '#/components/schemas/Address' addressTag: $ref: '#/components/schemas/AddressTag' metadata: $ref: '#/components/schemas/PaymentRefundAddressMetadata' identity: $ref: '#/components/schemas/PaymentRefundAddressIdentity' ownership: $ref: '#/components/schemas/PaymentRefundAddressOwnership' status: $ref: '#/components/schemas/PaymentRefundAddressStatus' createDate: $ref: '#/components/schemas/UtcTimestamp' updateDate: $ref: '#/components/schemas/UtcTimestamp' IdempotencyKey: type: string description: >- Universally unique identifier (UUID v4) idempotency key. This key is utilized to ensure exactly-once execution of mutating requests. format: uuid example: ba943ff1-ca16-49b2-ba55-1057e70ca5c7 Chain: type: string description: A blockchain that a given currency is available on. enum: - ALGO - APTOS - ARB - ARC - AVAX - BASE - BTC - CELO - CODEX - ETH - HBAR - HYPEREVM - INK - LINEA - NEAR - NOBLE - OP - PLUME - PAH - PLASMA - POLY - SEI - SOL - SONIC - SUI - UNI - WORLDCHAIN - XLAYER - XDC - XLM - XRP - ZKS Address: type: string description: > An alphanumeric string representing a blockchain address. Formatting varies by blockchain. Be sure to preserve the exact formatting and capitalization of the address. **Important:** For Ripple (XRP) addresses, only the classic address format is supported (for example, `rPEPPER7kfTD9w2To4CQk6UCfuHM9c6GDY`). The `x-address` format is NOT supported currently (for example, `XV5sbjUmgPpvXv4ixFWZ5ptAYZ6PD2q1qM6owqNbug8W6KV`). example: '0x8381470ED67C3802402dbbFa0058E8871F017A6F' AddressTag: type: string description: >- The secondary identifier for a blockchain address. An example of this is the memo field on the Stellar network, which can be text, id, or hash format. nullable: true example: '123456789' PaymentRefundAddressMetadata: type: object description: Metadata for a refund address. properties: nickname: type: string example: Refund recipient email: type: string example: satoshi@example.com bns: type: string example: sample.circle lei: type: string example: 529900T8BM49AURSDO55 PaymentRefundAddressOwnership: type: object required: - custody properties: type: type: string description: Ownership type for the refund address. enum: - third_party example: third_party custody: $ref: '#/components/schemas/PaymentRefundAddressCustody' Id: type: string description: Unique system generated identifier for the entity. format: uuid example: b8627ae8-732b-4d25-b947-1df8f4007a29 PaymentRefundAddressIdentity: type: object description: >- Recipient identity derived from the original payment's Travel Rule originator PII. Do not provide this object when creating a refund address. properties: type: type: string enum: - individual - business example: individual firstName: type: string example: John lastName: type: string example: Doe businessName: type: string example: Example Trading Pte. Ltd. individual: $ref: '#/components/schemas/PaymentRefundAddressIndividualIdentity' business: $ref: '#/components/schemas/PaymentRefundAddressBusinessIdentity' PaymentRefundAddressStatus: type: string description: Refund address status. enum: - pending - pending_verification - pending_additional_information - pending_owner_information - pending_beneficiary_information - denied - inactive - verification_succeeded - active - on_hold - failed - disabled example: pending UtcTimestamp: type: string description: ISO-8601 UTC date/time format. example: '2020-04-10T02:13:30.000Z' PaymentRefundAddressCustody: type: object required: - type - vaspId properties: type: type: string description: Custody type for the refund address. enum: - hosted example: hosted vaspId: type: string format: uuid description: >- Hosted VASP identifier. Must match the VASP associated with the original payment sender. example: 581b9b20-28e1-464d-a257-e408733d0857 PaymentRefundAddressIndividualIdentity: type: object properties: dateOfBirth: type: string example: '1990-11-29' nationality: type: string example: US addressLine1: type: string example: 123 Main St. addressLine2: type: string example: Apt 4B city: type: string example: Boston district: type: string example: MA postalCode: type: string example: '02110' country: type: string example: US governmentIssuedId: type: string example: A1234567 PaymentRefundAddressBusinessIdentity: type: object properties: addressLine1: type: string example: 1 Raffles Place addressLine2: type: string example: '#10-01' city: type: string example: Singapore district: type: string example: SG postalCode: type: string example: 48616 country: type: string example: SG businessRegistrationNumber: type: string example: 202000001A dateOfIncorporation: type: string example: '2020-01-15' countryOfIncorporation: type: string example: SG businessIdentificationNumber: type: string example: 202000001A headers: XRequestId: description: >- Universally unique identifier (UUID v4) for the request. Helpful for identifying a request when communicating with Circle support. schema: type: string format: uuid example: 2adba88e-9d63-44bc-b975-9b6ae3440dde responses: BadRequest: description: The request cannot be processed due to a client error. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: type: object title: BadRequest required: - code - message properties: code: type: integer example: 400 message: type: string example: Something went wrong. example: code: 400 message: Bad request. examples: response: value: code: 400 message: Bad request. NotAuthorized: description: >- The request has not been applied because it lacks valid authentication credentials. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: type: object title: NotAuthorized required: - code - message properties: code: type: integer example: 400 message: type: string example: Something went wrong. example: code: 401 message: Malformed authorization. examples: response: value: code: 401 message: Malformed authorization. Forbidden: description: >- The request provides authentication, but the authenticated user does not possess sufficient permissions for accessing this resource. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: type: object title: Forbidden required: - code - message properties: code: type: integer example: 400 message: type: string example: Something went wrong. example: code: 3 message: Forbidden examples: response: value: code: 3 message: Forbidden InternalServerError: description: Unexpected server error. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: type: object title: InternalServerError required: - code - message properties: code: type: integer example: 400 message: type: string example: Something went wrong. example: code: 500 message: Internal server error. examples: response: value: code: 500 message: Internal server error. securitySchemes: bearerAuth: type: http scheme: bearer ````