> ## 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. # Modify a recipient > Updates address book recipient metadata. ## OpenAPI ````yaml openapi/payouts.yaml patch /v1/addressBook/recipients/{id} openapi: 3.0.2 info: version: ${version} title: Crypto Payouts API description: >- The Circle Payouts API allows you to programmatically make fast, global payouts to your customers, vendors, and suppliers. Make payouts on supported blockchains. servers: - url: https://api-sandbox.circle.com - url: https://api.circle.com security: [] tags: - name: Payouts description: Create and get information on address book payouts. - name: Crypto Address Book description: Manage blockchain addresses with metadata. paths: /v1/addressBook/recipients/{id}: patch: tags: - Crypto Address Book summary: Modify a recipient description: Updates address book recipient metadata. operationId: modifyAddressBookRecipient parameters: - $ref: '#/components/parameters/IdPath' requestBody: content: application/json: schema: $ref: '#/components/schemas/AddressBookRecipientModifyRequest' responses: '200': description: Successfully updated the address book recipient. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: title: ModifyAddressBookRecipientResponse properties: data: $ref: >- #/components/schemas/AddressBookRecipientModifyResponseData examples: response: value: data: id: 8755d0ea-14f9-4259-b092-de23c14b6568 chain: ETH address: '0x45bfcf1a6289a0b77b4d3f7d12005a05949fd8c3' metadata: nickname: sample nickname email: satoshi@circle.com bns: sample.circle status: pending createDate: '2022-07-21T20:13:35.578678Z' updateDate: '2022-07-21T20:19:24.859052Z' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/NotAuthorized' '404': $ref: '#/components/responses/NotFound' security: - bearerAuth: [] components: parameters: IdPath: name: id description: Universally unique identifier (UUID v4) of a resource. in: path required: true schema: type: string format: uuid example: b3d9d2d5-4c12-4946-a09d-953e82fae2b0 schemas: AddressBookRecipientModifyRequest: type: object properties: metadata: $ref: '#/components/schemas/AddressBookRecipientMetadata' AddressBookRecipientModifyResponseData: description: > Recipient returned after a metadata update. The payload omits `identity` and `ownership` for all Circle entities. allOf: - $ref: '#/components/schemas/AddressBookRecipientResponseGeneral' - type: object properties: createDate: $ref: '#/components/schemas/UtcTimestamp' updateDate: $ref: '#/components/schemas/UtcTimestamp' AddressBookRecipientMetadata: type: object description: > Recipient metadata. For Singapore (CIRCLE_SG) customers creating a self-hosted (`ownership.custody.type` = `self_hosted`) entry, `email` is required (validation error `2038`). properties: nickname: type: string description: Nickname related to the address. example: sample nickname email: allOf: - $ref: '#/components/schemas/Email' - description: >- Email address of the recipient. Required for Singapore (CIRCLE_SG) self-hosted entries. bns: type: string description: Blockchain Name Service (e.g. ENS) domain for the address. example: sample.circle AddressBookRecipientResponseGeneral: type: object properties: id: $ref: '#/components/schemas/Id' chain: $ref: '#/components/schemas/Chain' address: $ref: '#/components/schemas/Address' addressTag: $ref: '#/components/schemas/AddressTag' metadata: $ref: '#/components/schemas/AddressBookRecipientMetadata' status: type: string description: Status of the address book recipient. enum: - pending - pending_verification - inactive - active - denied UtcTimestamp: type: string description: ISO-8601 UTC date/time format. example: '2020-04-10T02:13:30.000Z' Email: type: string description: Email of the user. maxLength: 1024 example: satoshi@circle.com Id: type: string description: Unique system generated identifier for the entity. format: uuid example: b8627ae8-732b-4d25-b947-1df8f4007a29 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' 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. NotFound: description: The specified resource was not found. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: type: object title: NotFound required: - code - message properties: code: type: integer example: 400 message: type: string example: Something went wrong. example: code: 404 message: Not found. examples: response: value: code: 404 message: Not found. securitySchemes: bearerAuth: type: http scheme: bearer ````