> ## 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. # Upload a payout RFI file > Uploads a file in response to an active RFI file requirement for the specified fiat payout. The `fileKey` in `fileMetadata` must match one of the `fileKey` values from the `fileRequirements` array returned by `GET /v1/payouts/{id}/rfi`. **Encryption** — required for BFI-generated RFIs, optional for internally-generated RFIs: Check whether `GET /v1/payouts/{id}/rfi` returns a non-null `certificate` field: - **`certificate` present** (BFI-generated RFI): encrypt the file client-side before upload. 1. Extract `certificate.jwk` — an EC public key in JWK format. 2. Generate a random AES-128 key and encrypt the file bytes using **AES-128-GCM**. Retain the IV. 3. Wrap the AES-128 key using **ECDH-ES + AES-128 Key Wrap** (`ECDH-ES+A128KW` / `A128GCM`) against the EC public key from step 1. This produces a **Compact JWE string** (`header.encryptedKey.iv.ciphertext.tag`). 4. Submit with all three multipart fields (`fileMetadata`, `encryption`, `encryptedFile`). - **`certificate` absent** (internally-generated RFI): omit `encryption` and `encryptedFile`. Submit only `fileMetadata` and the raw `file` field. The file is stored with standard encryption-at-rest; no client-side encryption step is needed. ## OpenAPI ````yaml openapi/payouts.yaml post /v1/payouts/{id}/rfi/files 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/payouts/{id}/rfi/files: post: tags: - Payouts summary: Upload a payout RFI file description: > Uploads a file in response to an active RFI file requirement for the specified fiat payout. The `fileKey` in `fileMetadata` must match one of the `fileKey` values from the `fileRequirements` array returned by `GET /v1/payouts/{id}/rfi`. **Encryption** — required for BFI-generated RFIs, optional for internally-generated RFIs: Check whether `GET /v1/payouts/{id}/rfi` returns a non-null `certificate` field: - **`certificate` present** (BFI-generated RFI): encrypt the file client-side before upload. 1. Extract `certificate.jwk` — an EC public key in JWK format. 2. Generate a random AES-128 key and encrypt the file bytes using **AES-128-GCM**. Retain the IV. 3. Wrap the AES-128 key using **ECDH-ES + AES-128 Key Wrap** (`ECDH-ES+A128KW` / `A128GCM`) against the EC public key from step 1. This produces a **Compact JWE string** (`header.encryptedKey.iv.ciphertext.tag`). 4. Submit with all three multipart fields (`fileMetadata`, `encryption`, `encryptedFile`). - **`certificate` absent** (internally-generated RFI): omit `encryption` and `encryptedFile`. Submit only `fileMetadata` and the raw `file` field. The file is stored with standard encryption-at-rest; no client-side encryption step is needed. operationId: uploadPayoutRfiFiles parameters: - $ref: '#/components/parameters/IdPath' requestBody: required: true content: multipart/form-data: schema: type: object required: - fileMetadata properties: fileMetadata: type: object required: - fileName - fileType - fileKey properties: fileName: type: string description: Original file name including extension. example: invoice.pdf fileType: type: string description: MIME type of the file. example: application/pdf fileKey: type: string description: > Key identifying which file requirement this upload satisfies. Must match a `fileKey` value from `GET /v1/payouts/{id}/rfi` → `fileRequirements`. example: proofOfFunds encryption: type: object description: > JWE encryption envelope. Required when `certificate` is present in the RFI response (BFI-generated RFI). Omit for internally-generated RFIs. required: - encryptedAesKey - iv properties: encryptedAesKey: type: string description: > Compact JWE string wrapping the AES-128 file-encryption key. Algorithm: `ECDH-ES+A128KW` (key agreement) with `A128GCM` (content encryption). The recipient EC public key is obtained from `certificate.jwk` in the RFI response. example: >- eyJhbGciOiJFQ0RILUVTIn0..GawgguFyGrWKav7AX4VKUg.p0oLHRPhFBZqYYQxouP9gw.0HFmhOzsQ98HboVlPPyQ0A iv: type: string description: >- Base64-encoded AES-128-GCM initialization vector (96-bit / 12 bytes). example: YWJjZGVmZ2hpamts encryptedFile: type: string format: binary description: > AES-128-GCM encrypted file contents. Required when `encryption` is present (BFI-generated RFI). Omit for internally-generated RFIs. file: type: string format: binary description: > Raw (unencrypted) file contents. Required for internally-generated RFIs (when `certificate` is absent in the RFI response). Omit for BFI-generated RFIs. responses: '204': description: File uploaded successfully. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' '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 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 ````