> ## 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 settlement advance Permit2 typed data for signing > Returns Permit2 typed-data the maker signs to authorize delegate funding of their side of a trade. The witness is a `DelegateFundingAuthorization` with `permitted.amount = 0` -- Permit2 is used purely as an authorization carrier, no tokens transfer from the maker. Stateless: no persistence, no side effects. ## OpenAPI ````yaml openapi/stablefx.yaml post /v1/exchange/stablefx/signatures/settlementAdvances/presign openapi: 3.1.0 info: title: StableFX API description: > The StableFX API provides endpoints for trading stablecoins. ## Authentication All API requests require authentication using an API key. ## Base URL The base URL for all API endpoints is: `https://api.circle.com/v1/exchange/stablefx` version: 1.0.0 servers: - url: https://api.circle.com description: StableFX API server security: - BearerAuth: [] tags: - name: Quotes description: Endpoints for creating and managing quotes - name: Trades description: Endpoints for creating and managing trades - name: Signatures description: Endpoints for retrieving presign typed data and registering signatures - name: Fees description: Endpoints for retrieving fees - name: Funding description: Endpoints for funding trades - name: Webhook Subscriptions description: Manage subscriptions to notifications - name: Settlement Advance description: Request, track, and repay settlement advances. paths: /v1/exchange/stablefx/signatures/settlementAdvances/presign: post: tags: - Signatures summary: Get settlement advance Permit2 typed data for signing description: > Returns Permit2 typed-data the maker signs to authorize delegate funding of their side of a trade. The witness is a `DelegateFundingAuthorization` with `permitted.amount = 0` -- Permit2 is used purely as an authorization carrier, no tokens transfer from the maker. Stateless: no persistence, no side effects. operationId: presignSettlementAdvance requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/PresignSettlementAdvance' responses: '200': description: Typed-data ready for the maker to sign. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/SettlementAdvancePresign' '400': description: Invalid request or trade state. content: application/json: schema: $ref: '#/components/schemas/Error' '404': description: Trade not found. content: application/json: schema: $ref: '#/components/schemas/Error' security: - BearerAuth: [] components: schemas: PresignSettlementAdvance: type: object description: Request body for getting settlement advance Permit2 typed-data. required: - tradeId properties: tradeId: type: string description: Trade identifier. example: trade-abc-123 SettlementAdvancePresign: type: object description: Settlement advance Permit2 typed-data for maker signing. required: - advance - collateral - makerPermitTypedData properties: advance: $ref: '#/components/schemas/SettlementAdvanceCurrencyAmount' collateral: $ref: '#/components/schemas/SettlementAdvanceCurrencyAmount' makerPermitTypedData: $ref: '#/components/schemas/Permit2TypedData' Error: title: Error type: object required: - code - message properties: code: $ref: '#/components/schemas/ErrorCode' message: type: string description: Human-readable message that describes the error. example: Unknown error occurred errors: type: array description: Array of detailed error descriptions items: $ref: '#/components/schemas/DescriptiveError' XRequestId: type: string description: >- A unique identifier, which can be helpful for identifying a request when communicating with Circle support. example: 2adba88e-9d63-44bc-b975-9b6ae3440dde format: uuid SettlementAdvanceCurrencyAmount: type: object description: Currency and amount for settlement advance flows. required: - currency - amount properties: currency: $ref: '#/components/schemas/SettlementAdvanceCurrency' amount: $ref: '#/components/schemas/Amount' Permit2TypedData: type: object description: EIP-712 Permit2 typed-data envelope for trader signing. required: - types - primaryType - domain - message properties: types: type: object additionalProperties: type: array items: $ref: '#/components/schemas/EIP712TypeProperty' primaryType: type: string example: DelegateFundingAuthorizationPermitWitnessTransferFrom domain: $ref: '#/components/schemas/Permit2EIP712Domain' message: $ref: '#/components/schemas/DelegateFundingPermit2' ErrorCode: title: ErrorCode type: integer description: The code that corresponds to the error. enum: - -1 - 0 - 1 - 2 - 3 - 400 - 401 - 403 - 404 DescriptiveError: title: DescriptiveError type: object required: - error - message properties: error: $ref: '#/components/schemas/DescriptiveErrorType' location: type: - string - 'null' description: The key or path where the error occurred message: type: string description: Detailed description of the error SettlementAdvanceCurrency: type: string description: Currency code for settlement advance flows. example: USDC Amount: type: string pattern: ^\d+(?:\.\d{1,6})?$ description: Amount of currency, formatted as a string with up to six decimal places. example: '100.00' EIP712TypeProperty: type: object description: A single property definition in EIP-712 types required: - name - type properties: name: type: string description: The name of the property type: type: string description: The type of the property Permit2EIP712Domain: type: object description: Permit2 EIP-712 domain separator required: - name - chainId - verifyingContract properties: name: type: string description: The name of the signing domain example: Permit2 chainId: type: integer description: The chain ID of the network example: 11155111 verifyingContract: type: string description: The address of the verifying contract example: '0xffd21ca8F0876DaFAD7de09404E0c1f868bbf1AE' DelegateFundingPermit2: type: object description: >- Permit2 PermitWitnessTransferFrom payload with DelegateFundingAuthorization witness. The `permitted.amount` is always 0 -- Permit2 is used as an authorization carrier, no tokens transfer from the trader. required: - permitted - spender - nonce - deadline - witness properties: permitted: $ref: '#/components/schemas/TokenPermissions' spender: type: string description: FxEscrow contract address. example: 0xFxEscrow000000000000000000000000000000000 nonce: type: string description: Permit2 nonce, as a string representation of a uint256. example: '1234567890' deadline: type: string description: >- Permit2 deadline (unix timestamp), as a string representation of a uint256. example: '1782556800' witness: $ref: '#/components/schemas/DelegateFundingAuthorization' DescriptiveErrorType: title: DescriptiveErrorType type: string enum: - MISSING_OR_INVALID_FIELD description: Type of descriptive error TokenPermissions: type: object description: Token permissions for Permit2 required: - token - amount properties: token: type: string description: The token contract address example: 0xTOKEN amount: type: string description: >- The amount of tokens permitted, as a string representation of a uint256. example: '1000' DelegateFundingAuthorization: type: object description: >- DelegateFundingAuthorization witness binding the Permit2 authorization to a specific trade, funder, recipient, token, and amount. required: - id - funder - recipient - token - amount properties: id: type: string description: On-chain trade id (uint256). example: '987654321' funder: type: string description: >- Address of the funder wallet (Circle-controlled) authorized to deliver tokens on the trader's behalf. example: 0xLLCFunderPW...address recipient: type: string description: Address that receives the delivered tokens. example: 0xLLCEscrowPW...address token: type: string description: ERC-20 contract address of the token to be delivered. example: 0xMXNB...address amount: type: string description: >- Amount to be delivered by the funder, in token units (uint256, no decimals). Tokens use 6 decimal places, so 5000.00 MXNB is represented as "5000000000". example: '5000000000' 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' securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: PREFIX:ID:SECRET description: >- Circle's API Keys are formatted in the following structure "PREFIX:ID:SECRET". All three parts are requred to make a successful request. ````