> ## 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 USDC transfer quote > Returns a signed, time-bound fee quote for a native USDC transfer. A quote prices the fees a caller must pay and includes a `signedQuote` blob that the `TokenMessengerWithFees` contract verifies onchain. The `requests` array selects which fees to price: a `FORWARD` request prices destination-chain forwarding, while a `PRE_FINALITY` request prices faster-than-finality settlement. Include at most one request per type. ## OpenAPI ````yaml openapi/cctp.yaml post /v2/quote/burn/usdc/{sourceDomainId}/{destDomainId} openapi: 3.0.2 info: version: '1.0' title: Cross-Chain Transfer Protocol (CCTP) description: > Circle's Cross-Chain Transfer Protocol enables you to build seamless user experiences for sending and transacting USDC natively across blockchains. CCTP endpoints enable advanced capabilities such as fetching attestations for faster-than-finality burn events, verifying public keys across versions, accessing transaction details, querying Fast Transfer allowances and fees, and initiating re-attestation processes. servers: - url: https://iris-api-sandbox.circle.com - url: https://iris-api.circle.com security: [] tags: - name: CCTP description: Cross-Chain Transfer Protocol endpoints - name: CCTP V1 (Legacy) description: Legacy Cross-Chain Transfer Protocol endpoints - name: Quotes description: Signed, time-bound fee quotes for USDC transfers paths: /v2/quote/burn/usdc/{sourceDomainId}/{destDomainId}: post: tags: - Quotes summary: Create a USDC transfer quote description: > Returns a signed, time-bound fee quote for a native USDC transfer. A quote prices the fees a caller must pay and includes a `signedQuote` blob that the `TokenMessengerWithFees` contract verifies onchain. The `requests` array selects which fees to price: a `FORWARD` request prices destination-chain forwarding, while a `PRE_FINALITY` request prices faster-than-finality settlement. Include at most one request per type. operationId: createUsdcBurnQuote parameters: - name: sourceDomainId in: path required: true description: >- Source domain identifier for the blockchain the transfer starts from. Must be an EVM blockchain where upfront fees are supported, and must satisfy the applicable source-side requirements for included request types. For example, a `PRE_FINALITY` request requires a source blockchain where Fast Transfer is supported. schema: type: integer minimum: 0 example: 0 - name: destDomainId in: path required: true description: >- Destination domain identifier for the blockchain the transfer settles on. Must differ from `sourceDomainId` and must satisfy the applicable destination-side requirements for included request types. For example, a `FORWARD` request requires a destination blockchain where the Forwarding Service is supported. schema: type: integer minimum: 0 example: 1 requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreateUsdcBurnQuoteRequest' examples: nativeGasFeeToken: summary: Fees paid in the source-chain native gas token description: >- Uses the zero address for `feeToken`, so fees are priced in the source-chain native gas token. value: amount: '1000000' feeToken: '0x0000000000000000000000000000000000000000' requests: - type: FORWARD - type: PRE_FINALITY usdcFeeToken: summary: Fees paid in USDC description: >- Prices fees in USDC by setting `feeToken` to the source-chain USDC address (Ethereum mainnet USDC shown here). value: amount: '1000000' feeToken: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48' requests: - type: FORWARD responses: '200': description: Successfully created a signed USDC transfer quote. content: application/json: schema: $ref: '#/components/schemas/UsdcBurnQuoteResponse' '400': description: >- The request is invalid, references an unknown domain or fee token, or specifies an unsupported route. content: application/json: schema: $ref: '#/components/schemas/QuoteErrorResponse' '403': description: The requested transaction type is not authorized for this route. content: application/json: schema: $ref: '#/components/schemas/QuoteErrorResponse' '422': description: >- The pre-finality fee is unavailable or the allowance is insufficient for this route. content: application/json: schema: $ref: '#/components/schemas/QuoteErrorResponse' '503': description: >- The quote service is not configured or enabled, or is temporarily unavailable. content: application/json: schema: $ref: '#/components/schemas/QuoteErrorResponse' components: schemas: CreateUsdcBurnQuoteRequest: title: CreateUsdcBurnQuoteRequest type: object description: >- Specifies the transfer amount, fee token, and fees to price for a USDC transfer quote. additionalProperties: false required: - amount - requests properties: amount: type: string pattern: ^[1-9]\d*$ description: >- The transfer amount in USDC minor units, as a positive decimal integer string. example: '1000000' feeToken: type: string pattern: ^0x[a-fA-F0-9]{40}$ description: >- The token used to pay fees, as a source-chain EVM address. Defaults to the zero address, which requests fees in the source-chain native gas token. default: '0x0000000000000000000000000000000000000000' requests: type: array minItems: 1 maxItems: 2 description: >- The fees to price. Include a `FORWARD` request, a `PRE_FINALITY` request, or both. Each type may appear at most once. example: - type: FORWARD - type: PRE_FINALITY items: oneOf: - title: ForwardFeeRequest type: object description: Prices destination-chain forwarding of the transfer. additionalProperties: false required: - type properties: type: type: string enum: - FORWARD description: >- Requests a Forwarding Service fee. The destination blockchain must support the Forwarding Service. params: type: object description: Forwarding parameters. Defaults to an empty object. additionalProperties: false properties: hookData: type: string pattern: ^0x([a-fA-F0-9]{2})*$ description: >- Optional hook data to execute on the destination chain, as 0x-prefixed even-length hexadecimal. If supplied, it must contain forwarding hook data (with `cctp-forward` magic bytes). Omit to price the destination chain's default forwarding behavior. destinationCaller: type: string pattern: ^0x([a-fA-F0-9]{40}|[a-fA-F0-9]{64})$ description: >- The address authorized to finalize the transfer on the destination chain, as a 20-byte EVM address or a 32-byte value. Defaults to the zero address, which authorizes any caller. default: '0x0000000000000000000000000000000000000000' - title: PreFinalityFeeRequest type: object description: Prices faster-than-finality settlement. additionalProperties: false required: - type properties: type: type: string enum: - PRE_FINALITY description: >- Requests a Fast Transfer fee. The source blockchain must support Fast Transfer. UsdcBurnQuoteResponse: title: UsdcBurnQuoteResponse type: object description: A signed, time-bound fee quote for a USDC transfer. required: - signedQuote - issuedAt - expiry - feeTotalAmount - feeToken - items - nonce properties: signedQuote: type: string pattern: ^0x([a-fA-F0-9]{2})*$ description: >- The signed quote blob to submit to the `TokenMessengerWithFees` contract. example: '0xabcdef' issuedAt: type: integer description: >- The server time the quote was issued, as a Unix timestamp in seconds. Compute remaining validity relative to this value rather than the client clock. example: 1735689540 expiry: oneOf: - title: TimestampExpiry type: object description: The quote's expiry when it is encoded as a wall-clock time. required: - mode - expiresAt properties: mode: type: string enum: - TIMESTAMP description: The expiry encoding used by this quote. expiresAt: type: integer description: >- The exact wall-clock time at which the quote expires, as a Unix timestamp in seconds. example: 1735689600 - title: BlockNumberExpiry type: object description: >- The quote's expiry when it is encoded as a source-chain block number. required: - mode - expiresAtBlock - blockEstimatedAt properties: mode: type: string enum: - BLOCK_NUMBER description: The expiry encoding used by this quote. expiresAtBlock: type: integer description: >- The authoritative source-chain block at which the quote expires. example: 21000000 blockEstimatedAt: type: integer description: >- An advisory wall-clock estimate of when `expiresAtBlock` is reached, as a Unix timestamp in seconds, assuming the configured block time. example: 1735689600 description: > The quote's expiry. The `mode` field discriminates the shape: `TIMESTAMP` exposes an exact wall-clock `expiresAt`, while `BLOCK_NUMBER` exposes the authoritative onchain `expiresAtBlock` alongside an advisory `blockEstimatedAt`. feeTotalAmount: type: string description: >- The total fee across all items, in the fee token's minor units, as a decimal integer string. example: '1000' feeToken: type: string pattern: ^0x[a-fA-F0-9]{40}$ description: >- The token the fees are denominated in, as a source-chain EVM address. example: '0x0000000000000000000000000000000000000000' items: type: array description: The individual fees that sum to `feeTotalAmount`, one per fee type. items: type: object description: A single priced fee within the quote. required: - type - amount - args - argsHash properties: type: type: string enum: - FORWARD - PRE_FINALITY description: The fee category this item prices. amount: type: string description: >- The fee amount in the fee token's minor units, as a decimal integer string. example: '1000' args: type: array description: >- The ABI-encoded arguments the `TokenMessengerWithFees` contract verifies for this item. items: type: string example: - >- 0x0000000000000000000000000000000000000000000000000000000000000001 argsHash: type: string pattern: ^0x[a-fA-F0-9]{64}$ description: The keccak-256 hash of `args` as a 32-byte hexadecimal string. example: >- 0x1234567890123456789012345678901234567890123456789012345678901234 nonce: type: string description: >- Reserved for future use as a unique identifier for the quote. The `TokenMessengerWithFees` contract currently enforces a zero nonce. example: '0' metadata: type: object description: >- Optional pricing metadata. Present when exchange-rate conversion was applied. required: - exchangeRates properties: exchangeRates: type: object required: - feeTokenUsd - destinationTokenUsd properties: feeTokenUsd: type: string description: The USD price of the fee token used for conversion. example: '1.00' destinationTokenUsd: type: string description: The USD price of the destination token used for conversion. example: '1.00' QuoteErrorResponse: title: QuoteErrorResponse type: object description: A Quote API error. required: - errorCode - error properties: errorCode: type: string description: A stable, client-facing error identifier. enum: - UNKNOWN_DOMAIN - UNSUPPORTED_ROUTE - UNSUPPORTED_FEE_TOKEN - SERVICE_NOT_CONFIGURED - SERVICE_NOT_ENABLED - RPC_UNAVAILABLE - PRICING_UNAVAILABLE - PRE_FINALITY_UNAVAILABLE - PRE_FINALITY_INSUFFICIENT_ALLOWANCE - INVALID_PAYLOAD - UNAUTHORIZED_TRANSACTION_TYPE - UNSUPPORTED_CHAIN - UNSUPPORTED_WORKFLOW - VALIDATION_ERROR example: VALIDATION_ERROR error: type: string description: A human-readable description of the error. example: Source and destination domain cannot be the same ````