> ## 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. # List crypto payment customers > Lists Travel Rule customers for eligible Circle Singapore (`CIRCLE_SG`) merchants. List responses omit customer PII. ## OpenAPI ````yaml openapi/payments.yaml get /v1/payments/customers 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/customers: get: tags: - Crypto Payment Customers summary: List crypto payment customers description: > Lists Travel Rule customers for eligible Circle Singapore (`CIRCLE_SG`) merchants. List responses omit customer PII. operationId: listPaymentCustomers parameters: - name: refId description: Filters customers by merchant-supplied reference ID. in: query required: false schema: type: string - $ref: '#/components/parameters/PageBefore' - $ref: '#/components/parameters/PageAfter' - $ref: '#/components/parameters/PageSize' responses: '200': description: Successfully retrieved customers. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: title: ListPaymentCustomersResponse properties: data: type: array items: $ref: '#/components/schemas/PaymentCustomerListItem' examples: customers: value: data: - id: 7d4f71c1-7e2e-4a1d-9df3-3a4d8d6d5a11 refId: 310c458a-18eb-4cbd-8a9a-586d9448ae69 type: individual status: approved '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/NotAuthorized' '403': $ref: '#/components/responses/Forbidden' '500': $ref: '#/components/responses/InternalServerError' security: - bearerAuth: [] components: parameters: PageBefore: name: pageBefore description: > A collection ID value used for pagination. It marks the exclusive end of a page. When provided, the collection resource will return the next `n` items before the id, with `n` being specified by `pageSize`. The items will be returned in the natural order of the collection. The resource will return the first page if neither `pageAfter` nor `pageBefore` are specified. SHOULD NOT be used in conjuction with pageAfter. in: query required: false schema: type: string PageAfter: name: pageAfter description: > A collection ID value used for pagination. It marks the exclusive begin of a page. When provided, the collection resource will return the next `n` items after the id, with `n` being specified by `pageSize`. The items will be returned in the natural order of the collection. The resource will return the first page if neither `pageAfter` nor `pageBefore` are specified. SHOULD NOT be used in conjuction with pageBefore. in: query required: false schema: type: string PageSize: name: pageSize description: > Limits the number of items to be returned. Some collections have a strict upper bound that will disregard this value. In case the specified value is higher than the allowed limit, the collection limit will be used. If avoided, the collection will determine the page size itself. in: query required: false schema: type: integer minimum: 1 example: 5 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 schemas: PaymentCustomerListItem: type: object description: Travel Rule customer summary. List responses omit customer PII. required: - id - refId - type - status properties: id: $ref: '#/components/schemas/Id' refId: type: string format: uuid description: Merchant-supplied customer reference. Must be a UUID. example: 310c458a-18eb-4cbd-8a9a-586d9448ae69 type: $ref: '#/components/schemas/PaymentCustomerType' status: $ref: '#/components/schemas/PaymentCustomerStatus' Id: type: string description: Unique system generated identifier for the entity. format: uuid example: b8627ae8-732b-4d25-b947-1df8f4007a29 PaymentCustomerType: type: string description: Customer type. enum: - individual - business example: individual PaymentCustomerStatus: type: string description: Customer screening status. enum: - pending - approved - rejected example: pending 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 ````