> ## 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. # Complete a social session > Non-custodial accounts are available in sandbox only. Production non-custodial accounts are on the roadmap. Verifies the identity provider's ID token against a prepared login and links the signed-in identity to the end customer named by `clientEntityId`. Returns a single-use `registrationHandle` for `POST /v1/accounts/auth/deviceKeyRegistration`. Before you go live, register your application's Google client IDs in Circle Hub (Digital Asset Accounts settings > Social login). In staging and production, the ID token's audience must be one of them. This call doesn't create an account or a wallet, and doesn't need a device signature. The Digital Asset Accounts SDK builds the request on the device. Your backend relay adds your API key and forwards it. ## OpenAPI ````yaml openapi/accounts.yaml post /v1/accounts/auth/sessions 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: Contract Executions description: >- Execute EVM contract calls from non-custodial accounts and track their results. - 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: Device Authentication description: > Sign in end users of non-custodial accounts with a social login, and register the authorization key that signs their non-custodial requests. The Digital Asset Accounts SDK builds these requests on the end user's device, and your backend relay forwards them with your API key. - 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/accounts/auth/sessions: post: tags: - Device Authentication summary: Complete a social session description: > Non-custodial accounts are available in sandbox only. Production non-custodial accounts are on the roadmap. Verifies the identity provider's ID token against a prepared login and links the signed-in identity to the end customer named by `clientEntityId`. Returns a single-use `registrationHandle` for `POST /v1/accounts/auth/deviceKeyRegistration`. Before you go live, register your application's Google client IDs in Circle Hub (Digital Asset Accounts settings > Social login). In staging and production, the ID token's audience must be one of them. This call doesn't create an account or a wallet, and doesn't need a device signature. The Digital Asset Accounts SDK builds the request on the device. Your backend relay adds your API key and forwards it. operationId: completeSocialSession requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SocialSessionRequest' examples: request: summary: Request value: idempotencyKey: 8a2b3c4d-5e6f-4a7b-9c8d-0e1f2a3b4c5d loginRequestId: 3f9a6c1e-2b7d-4e8a-9c0f-5d1e2a3b4c5d idToken: >- eyJhbGciOiJSUzI1NiIsImtpZCI6IjEifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20ifQ.c2lnbmF0dXJl clientEntityId: a3f1b2c4-d5e6-7890-abcd-ef1234567890 responses: '200': description: Successfully verified the social login. headers: X-Request-Id: $ref: '#/components/headers/XRequestId' content: application/json: schema: $ref: '#/components/schemas/SocialSessionResponse' examples: response: summary: Response value: data: registrationHandle: Yk3vQ9xR2mT7nL4pW8sZ1cF6hJ0aD5eG3uB9iK2oN7q clientEntityId: a3f1b2c4-d5e6-7890-abcd-ef1234567890 expiresAt: 1759766760000 '400': description: > The request can't be processed. For example, `clientEntityId` is missing, or it isn't one of your end customers (error code 420001). content: application/json: schema: $ref: '#/components/schemas/Error' '401': $ref: '#/components/responses/NotAuthorized' '403': description: > The social login couldn't be verified (error code 420037). For example, the ID token is invalid or doesn't carry the prepared nonce, the ID token's audience isn't a client ID registered for your entity in Circle Hub, the login request doesn't belong to your entity, or the identity provider reports that the signed-in identity is already linked to a different `clientEntityId`. content: application/json: schema: $ref: '#/components/schemas/Error' '409': description: > The `idempotencyKey` was already used with a different request body (error code 420034), or the login request was already used for a session (error code 420039). Start again with a new prepared login. content: application/json: schema: $ref: '#/components/schemas/Error' '410': description: > The login request has expired (error code 420035). Start again with a new prepared login. content: application/json: schema: $ref: '#/components/schemas/Error' '413': description: | The request body is larger than 64 KiB (error code 420067). content: application/json: schema: $ref: '#/components/schemas/Error' '500': $ref: '#/components/responses/InternalServerError' security: - bearerAuth: [] components: schemas: SocialSessionRequest: type: object additionalProperties: false required: - idempotencyKey - loginRequestId - idToken - clientEntityId properties: idempotencyKey: $ref: '#/components/schemas/IdempotencyKey' loginRequestId: type: string format: uuid description: > The `loginRequestId` returned by `POST /v1/accounts/auth/loginRequests`. example: 3f9a6c1e-2b7d-4e8a-9c0f-5d1e2a3b4c5d idToken: type: string description: > The ID token your application received from the identity provider. It must carry the `oidcNonce` returned when the login was prepared. maxLength: 8192 example: >- eyJhbGciOiJSUzI1NiIsImtpZCI6IjEifQ.eyJpc3MiOiJodHRwczovL2FjY291bnRzLmdvb2dsZS5jb20ifQ.c2lnbmF0dXJl clientEntityId: type: string format: uuid description: > The end customer the signed-in end user acts for. Use the `clientEntityId` returned when you created the end customer with [Create a partner client](https://developers.circle.com/api-reference/end-user-onboarding/create-partner-client) (`POST /v1/partner/clients`). It must belong to your entity. Circle permanently links the signed-in identity to this `clientEntityId`, and you can't change the link later. Read the value from your own backend session for the signed-in user. Never take it from user input. example: a3f1b2c4-d5e6-7890-abcd-ef1234567890 SocialSessionResponse: type: object required: - data additionalProperties: false properties: data: $ref: '#/components/schemas/SocialSession' 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' IdempotencyKey: type: string description: >- Universally unique identifier (UUID v4) idempotency key. This key is utilized to ensure exactly-once execution of mutating requests. format: uuid example: ba943ff1-ca16-49b2-ba55-1057e70ca5c7 XRequestId: type: string format: uuid example: 2adba88e-9d63-44bc-b975-9b6ae3440dde SocialSession: type: object description: A verified social session, ready for device registration. required: - registrationHandle - clientEntityId - expiresAt properties: registrationHandle: type: string description: > Single-use handle for `POST /v1/accounts/auth/deviceKeyRegistration`. Treat it as a secret: don't log or store it. example: Yk3vQ9xR2mT7nL4pW8sZ1cF6hJ0aD5eG3uB9iK2oN7q clientEntityId: type: string format: uuid description: > The end customer that the signed-in identity is linked to. Matches the `clientEntityId` you sent. example: a3f1b2c4-d5e6-7890-abcd-ef1234567890 expiresAt: description: > When the registration handle expires, 5 minutes after the session was created. Afterwards `POST /v1/accounts/auth/deviceKeyRegistration` returns `410` (error code 420035). allOf: - $ref: '#/components/schemas/AuthTimestamp' 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. AuthTimestamp: type: integer format: int64 description: A point in time, in milliseconds since the Unix epoch. example: 1759766400000 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: 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. 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 ````