> ## 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 an FX quote > Create a quote to swap USDC and EURC for an end user's account. Only USDC <> EURC swaps are supported. Tradable quotes that include a fiat currency are rejected. - `tradable` quotes lock a rate for a few seconds (until `expiry`). Execute one with Create an FX trade. Set `source` to the end user's account. - `reference` quotes return an indicative rate only and can't be traded. ## OpenAPI ````yaml openapi/accounts.yaml post /v1/exchange/quotes openapi: 3.1.0 info: version: 1.0.0 title: Accounts (Stablecoin) API description: > Circle's Accounts API provides endpoints for managing stablecoin accounts -- including transfers, withdrawals, deposits, wire and ACH bank accounts, and blockchain addresses. An **Account** is a general representation of a ledger or custody object that holds balances. It can be a business account, a stablecoin account ledger for an end user, an extra sub-ledger, or any future custody solution. license: name: Circle License url: https://circle.com/terms servers: - url: https://api-sandbox.circle.com - url: https://api.circle.com security: [] tags: - name: Accounts description: Manage accounts. - name: Account Groups description: Manage custody account groups and their memberships. - name: Limits description: View effective account limits and current usage. - name: Transfers description: > Move funds between accounts or out to a verified blockchain address, and track inbound and outbound onchain transfers. - name: Transactions description: | Get a unified, customer-friendly view of account transaction activity. - name: Wires description: Manage account bank accounts for wire transfers. - name: Deposits description: Get information on account bank deposits. - name: Withdrawals description: Manage account bank withdrawals (fiat offramp). - name: ACH description: Manage account bank accounts for ACH transfers. - name: Deposit Addresses description: Manage account deposit addresses. - name: Recipient Addresses description: Manage account recipient addresses used for transfers. - name: Passkeys description: > Manage WebAuthn passkeys and Strong Customer Authentication (SCA) challenges for end users. - name: Crypto Payments description: > Get crypto payments and crypto refunds received through payment intents. Available for Digital Asset Accounts only on custody accounts (`purpose: custody`), and only for third-party payments. Not supported when the distributor or the end user is under the Circle FR (`CIRCLE_FR`) or Circle SG (`CIRCLE_SG`) legal entity. - name: Crypto Payment Intents description: > Create, expire, refund, and track payment intents for receiving crypto payments. Available for Digital Asset Accounts only on custody accounts (`purpose: custody`), and only for third-party payments. Not supported when the distributor or the end user is under the Circle FR (`CIRCLE_FR`) or Circle SG (`CIRCLE_SG`) legal entity. - name: Crypto Payouts description: > Create and track crypto payouts to recipient addresses. Available for Digital Asset Accounts only on custody accounts (`purpose: custody`), and only for third-party payouts. Not supported when the distributor or the end user is under the Circle FR (`CIRCLE_FR`) or Circle SG (`CIRCLE_SG`) legal entity. - name: Crypto Address Book description: > Manage address book recipients used as crypto payout destinations. Available for Digital Asset Accounts only on custody accounts (`purpose: custody`), and only for third-party payouts. Not supported when the distributor or the end user is under the Circle FR (`CIRCLE_FR`) or Circle SG (`CIRCLE_SG`) legal entity. - name: FX Trades description: | Quote and execute USDC <> EURC swaps for end users' accounts. - name: FX Settlements description: Get settlements of FX trades. - name: Webhook Subscriptions description: Manage subscriptions to Digital Asset Accounts webhook notifications. - name: Webhooks description: | Webhook event payloads Circle sends to a subscribed endpoint. paths: /v1/exchange/quotes: post: tags: - FX Trades summary: Create an FX quote description: > Create a quote to swap USDC and EURC for an end user's account. Only USDC <> EURC swaps are supported. Tradable quotes that include a fiat currency are rejected. - `tradable` quotes lock a rate for a few seconds (until `expiry`). Execute one with Create an FX trade. Set `source` to the end user's account. - `reference` quotes return an indicative rate only and can't be traded. operationId: createFxQuote requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/FxQuoteCreationRequest' responses: '201': description: Successfully created a quote. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/CreateFxQuoteResponse' '400': $ref: '#/components/responses/CreateFxQuoteBadRequest' '401': $ref: '#/components/responses/NotAuthorized' '403': $ref: '#/components/responses/Forbidden' '500': $ref: '#/components/responses/InternalServerError' security: - bearerAuth: [] components: schemas: FxQuoteCreationRequest: type: object required: - from - to properties: type: type: string description: > The quote type. Use `tradable` to get a quote you can execute with Create an FX trade. Defaults to `reference`. enum: - reference - tradable default: reference example: tradable from: description: > Currency and, optionally, amount to sell. Exactly one of `from` and `to` must be USDC. Set at most one of `from.amount` and `to.amount`; `tradable` quotes require exactly one. Amounts must be at least `2.00` with at most 2 decimal places. allOf: - $ref: '#/components/schemas/FxOptionalAmountMoney' to: description: Currency and, optionally, amount to buy. allOf: - $ref: '#/components/schemas/FxOptionalAmountMoney' source: description: > Required for `tradable` quotes. The end user's account that is debited for the `from` amount. Ignored for `reference` quotes. allOf: - $ref: '#/components/schemas/FxLocation' destination: description: > The end user's account that is credited with the `to` amount. Must belong to the same client entity as `source`. Defaults to `source`. Ignored for `reference` quotes. allOf: - $ref: '#/components/schemas/FxLocation' CreateFxQuoteResponse: title: CreateFxQuoteResponse properties: data: $ref: '#/components/schemas/FxQuote' FxOptionalAmountMoney: type: object required: - currency properties: amount: type: string description: Magnitude of the amount, in units of the currency, with a `.`. example: '100.00' currency: $ref: '#/components/schemas/FxCurrency' FxLocation: type: object description: An end user's account that funds or receives one leg of a swap. required: - type - id properties: type: type: string enum: - wallet example: wallet id: type: string pattern: ^\d+$ description: > The numeric `accountId` of the end user's account, as returned by `GET /v1/accounts`. The account must be active and belong to one of your client entities, not to your own entity. example: '1000662322' description: type: string readOnly: true description: > Description of the account. Returned by Get an FX trade and List FX trades when it can be resolved; omitted otherwise. example: End User Wallet XRequestId: type: string format: uuid example: 2adba88e-9d63-44bc-b975-9b6ae3440dde FxQuote: type: object required: - id - rate - from - to - type properties: id: $ref: '#/components/schemas/Id' rate: type: number description: > Units of the `from` currency per one unit of the `to` currency, with Circle's spread included (`to.amount` is approximately `from.amount` / `rate`). Rounded up to 4 decimal places. example: 0.9259 from: $ref: '#/components/schemas/FxOptionalAmountMoney' to: $ref: '#/components/schemas/FxOptionalAmountMoney' type: type: string description: The quote type. enum: - reference - tradable example: tradable expiry: description: > Time after which the quote can no longer be traded. Tradable quotes only; they are valid for a few seconds. allOf: - $ref: '#/components/schemas/UtcTimestamp' timestamp: description: Time the quote was created. Reference quotes only. allOf: - $ref: '#/components/schemas/UtcTimestamp' estimatedSettlementTime: description: Estimated settlement time. Tradable quotes only. allOf: - $ref: '#/components/schemas/UtcTimestamp' source: description: Account debited for the `from` amount. Tradable quotes only. allOf: - $ref: '#/components/schemas/FxLocation' destination: description: > Account credited with the `to` amount. Tradable quotes only. Equals `source` when the request omitted `destination`. allOf: - $ref: '#/components/schemas/FxLocation' clientEntityId: type: string format: uuid description: > Client entity that owns `source` and `destination`. Tradable quotes only. example: a3f1b2c4-d5e6-7890-abcd-ef1234567890 Error: type: object required: - code - message properties: code: type: integer description: > Circle internal status code from the platform `CoreStatusCode` enum (and its domain-specific extensions). **This is not the HTTP status code** — `-1` is the catch-all unknown error, `1`/`2` indicate API parameter problems, `3` is forbidden, `4` is unauthorized, and larger values identify domain-specific failures. Consumers should rely on the HTTP status line for transport-level error class and on this field for the specific Circle error case. example: 2 message: type: string description: >- Internal error message; suitable for logging but not for end-user display. example: API parameter invalid. externalMessage: type: string description: > End-user-displayable error message. Present when the server has generated a customer-facing variant for this error; omitted otherwise. example: The provided amount exceeds the maximum allowed. errors: type: array description: Additional request-field validation errors, when available. items: $ref: '#/components/schemas/ErrorDetail' FxCurrency: type: string description: > Stablecoin on one leg of an FX swap. Digital Asset Accounts support USDC <> EURC swaps only. enum: - USDC - EURC example: EURC Id: type: string description: Unique system-generated identifier for the entity. format: uuid example: b8627ae8-732b-4d25-b947-1df8f4007a29 UtcTimestamp: type: string description: ISO-8601 UTC date/time format. example: '2020-04-10T02:13:30.000Z' ErrorDetail: type: object required: - error - message properties: error: type: string description: Machine-readable error identifier. example: invalid_value location: type: string description: Query parameter or request field that caused the error. example: assetType message: type: string description: Human-readable description of the specific error. example: The operation and assetType combination is invalid. headers: XRequestId: description: > Circle-generated universally unique identifier (UUID v4). Useful for identifying a specific request when communicating with Circle Support. schema: $ref: '#/components/schemas/XRequestId' responses: CreateFxQuoteBadRequest: description: The request cannot be processed due to a client error. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/Error' examples: missingSource: summary: >- Tradable quote without one of your end users' accounts as `source` value: code: 3025 message: The specified wallet is invalid for this request. fiatCurrency: summary: Tradable quote for a currency pair that includes a fiat currency value: code: 3008 message: At least one of the quote currencies is invalid. bothAmounts: summary: Both `from.amount` and `to.amount` set value: code: 3005 message: The quote amount is invalid. 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: $ref: '#/components/schemas/Error' example: code: 4 message: Unauthorized. Forbidden: description: The API key does not have permission to access this resource. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/Error' example: code: 3 message: Missing permission. InternalServerError: description: >- The server encountered an unexpected condition that prevented it from fulfilling the request. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/Error' example: code: -1 message: 'Something went wrong. errId: 1f0b0c455e40f753f07b4f0ae6abd4b4' securitySchemes: bearerAuth: type: http scheme: bearer ````