> ## 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. # List user operations > Retrieve a list of all user operations that fit the specified parameters. ## OpenAPI ````yaml openapi/buidl-wallets.yaml get /v1/w3s/buidl/userOps openapi: 3.0.3 info: description: Modular Wallets API documentation. title: Modular Wallets version: '1.0' servers: - url: https://api.circle.com security: - BearerAuth: [] tags: - name: Transfers - name: UserOps - name: Wallets paths: /v1/w3s/buidl/userOps: get: tags: - UserOps summary: List user operations description: >- Retrieve a list of all user operations that fit the specified parameters. operationId: listUserOps parameters: - name: blockchain description: Filter by the blockchain. in: query schema: $ref: '#/components/schemas/Blockchain' - name: refId description: Filter by the optional user-defined reference identifier. in: query schema: $ref: '#/components/schemas/ReferenceId' - name: senders description: Filter by the senders. in: query schema: $ref: '#/components/schemas/Addresses' - name: state description: Filter by the state. in: query schema: $ref: '#/components/schemas/UserOpState' - name: txHash description: Filter by the txHash. in: query schema: $ref: '#/components/schemas/TxHash' - name: userOpHash description: Filter by the userOpHash. in: query schema: $ref: '#/components/schemas/UserOpHash' - $ref: '#/components/parameters/From' - $ref: '#/components/parameters/To' - $ref: '#/components/parameters/PageBefore' - $ref: '#/components/parameters/PageAfter' - $ref: '#/components/parameters/PageSize' responses: '200': description: User operation list retrieved content: application/json: schema: $ref: '#/components/schemas/UserOps' headers: X-Request-Id: $ref: '#/components/headers/XRequestId' Link: $ref: '#/components/headers/PaginationLink' '400': $ref: '#/components/responses/DefaultError' '401': $ref: '#/components/responses/NotAuthorized' security: - BearerAuth: [] components: schemas: Blockchain: title: Blockchain type: string description: Blockchain network of resource. enum: - ETH - ETH-SEPOLIA - MATIC - MATIC-AMOY - ARB - ARB-SEPOLIA - UNI - UNI-SEPOLIA - BASE - BASE-SEPOLIA - OP - OP-SEPOLIA - AVAX - AVAX-FUJI - ARC - ARC-TESTNET - MONAD - MONAD-TESTNET example: MATIC-AMOY ReferenceId: type: string description: >- Optional user-defined reference identifier for the wallet. Not used by Circle for wallet functionality. Used for internal tracking or associating wallets with entities in your own systems (for example, a customer or account ID). example: customer_12345 Addresses: title: Addresses description: > A list of blockchain generated unique identifier, associated with wallet (account), smart contract or other blockchain objects, seperated by comma. type: string example: >- 0x4b6c0b0078b63f881503e7fd3a9a1061065db242,0x187785007d4a7D6756e834768597dA8fA6fcfE8a UserOpState: title: State type: string description: State of user operation. enum: - SENT - CONFIRMED - COMPLETE - FAILED example: COMPLETE TxHash: title: TxHash type: string description: Blockchain generated identifier of transaction. example: '0x4a25cc5e661d8504b59c5f38ba93f010e8518966f00e2ceda7955c4b8621357d' UserOpHash: title: UserOpHash type: string description: Generated identifier of user operation. example: '0x54d3cccda6ffa503bc1e554937fe67818b6ca1a5a05c7e66ebfa32bf27520152' UserOps: title: UserOpsResponse type: object required: - data properties: data: type: object required: - userOperations properties: userOperations: type: array description: All user operations that match criteria. items: $ref: '#/components/schemas/UserOp' UserOp: title: UserOp type: object required: - id - blockchain - state - userOpHash - userOperation properties: id: $ref: '#/components/schemas/Id' refId: $ref: '#/components/schemas/ReferenceId' actualGasCost: type: string description: Actual gas cost of user operation. example: '0.0015584763706281' actualGasUsed: type: string description: Actual gas used of user operation. example: '182385' blockDate: $ref: '#/components/schemas/BlockDate' blockHash: $ref: '#/components/schemas/BlockHash' blockHeight: $ref: '#/components/schemas/BlockHeight' blockchain: $ref: '#/components/schemas/Blockchain' errorReason: $ref: '#/components/schemas/UserOpErrorReason' revertReason: type: string description: On-chain failed revert reason of user operation. state: $ref: '#/components/schemas/UserOpState' to: $ref: '#/components/schemas/Address' description: Address of user operation executed with. txHash: $ref: '#/components/schemas/TxHash' userOpHash: $ref: '#/components/schemas/UserOpHash' userOperation: $ref: '#/components/schemas/UserOperation' createDate: $ref: '#/components/schemas/CreateDate' updateDate: $ref: '#/components/schemas/UpdateDate' XRequestId: type: string format: uuid description: >- A unique identifier, which can be helpful for identifying a request when communicating with Circle support. example: 2adba88e-9d63-44bc-b975-9b6ae3440dde Error: title: Error type: object required: - code - message properties: code: type: integer description: Code that corresponds to the error. message: type: string description: Message that describes the error. Id: type: string format: uuid description: System-generated unique identifier of the resource. example: c4d1da72-111e-4d52-bdbf-2e74a2d803d5 BlockDate: title: BlockDate type: string format: date-time description: Date and time of block, in ISO-8601 UTC format. example: '2023-01-01T12:04:05Z' BlockHash: title: BlockHash type: string description: Blockchain generated identifier of block. example: '0x2eb19fd02850ff963efefbaa71dbcd4acb41a9c261c4f8961979db1b56d48704' BlockHeight: title: BlockHeight type: integer description: Blockchain height of block. example: 123456 UserOpErrorReason: title: ErrorReason type: string description: Error reason of failed user operation. enum: - FAILED_ON_CHAIN - FAILED_REPLACED example: FAILED_REPLACED Address: title: Address description: > Blockchain generated unique identifier, associated with wallet (account), smart contract or other blockchain objects. type: string example: '0x4b6c0b0078b63f881503e7fd3a9a1061065db242' UserOperation: title: UserOperation type: object required: - callData - nonce - sender properties: callData: type: string callGasLimit: type: string factory: type: string factoryData: type: string initCode: type: string maxFeePerGas: type: string maxPriorityFeePerGas: type: string nonce: type: string paymaster: type: string paymasterAndData: type: string paymasterData: type: string paymasterPostOpGasLimit: type: string paymasterVerificationGasLimit: type: string preVerificationGas: type: string sender: type: string signature: type: string verificationGasLimit: type: string CreateDate: type: string format: date-time description: Date and time the resource was created, in ISO-8601 UTC format. example: '2023-01-01T12:04:05Z' UpdateDate: type: string format: date-time description: Date and time the resource was last updated, in ISO-8601 UTC format. example: '2023-01-01T12:04:05Z' parameters: From: name: from description: >- Queries items created since the specified date-time (inclusive) in ISO 8601 format. in: query schema: type: string format: date-time example: '2023-01-01T12:04:05Z' To: name: to description: >- Queries items created before the specified date-time (inclusive) in ISO 8601 format. in: query schema: type: string format: date-time example: '2023-01-01T12:04:05Z' PageBefore: name: pageBefore description: > A collection ID value used for pagination. It marks the exclusive end of a page. When provided, the collection resource will return the next n items before the id, with n being specified by pageSize. The items will be returned in the natural order of the collection. The resource will return the first page if neither pageAfter nor pageBefore are specified. SHOULD NOT be used in conjunction with pageAfter. in: query schema: type: string format: uuid PageAfter: name: pageAfter description: > A collection ID value used for pagination. It marks the exclusive begin of a page. When provided, the collection resource will return the next n items after the id, with n being specified by pageSize. The items will be returned in the natural order of the collection. The resource will return the first page if neither pageAfter nor pageBefore are specified. SHOULD NOT be used in conjunction with pageBefore. in: query schema: type: string format: uuid PageSize: name: pageSize description: > Limits the number of items to be returned. Some collections have a strict upper bound that will disregard this value. In case the specified value is higher than the allowed limit, the collection limit will be used. If avoided, the collection will determine the page size itself. in: query schema: type: integer default: 10 maximum: 50 minimum: 1 headers: XRequestId: description: > Developer-provided header parameter or Circle-generated universally unique identifier (UUID v4). Useful for identifying a specific request when communicating with Circle Support. schema: $ref: '#/components/schemas/XRequestId' PaginationLink: description: > Pagination cursor information. Format includes the following link relations: - self: URL pointing to the current page. - first: URL pointing to the first page. - next: URL pointing to the next page (omitted on the last page). - prev: URL pointing to the previous page (omitted on the first page). It's important to form calls with Link header values instead of constructing your own URLs. schema: type: string example: >- ; rel="next" responses: DefaultError: content: application/json: schema: $ref: '#/components/schemas/Error' description: Error response headers: X-Request-Id: $ref: '#/components/headers/XRequestId' NotAuthorized: content: application/json: schema: type: object title: NotAuthorizedResponse required: - code - message properties: code: type: integer description: Code that corresponds to the error. message: type: string description: Message that describes the error. example: code: 401 message: Malformed authorization. description: >- Request has not been applied because it lacks valid authentication credentials. headers: X-Request-Id: $ref: '#/components/headers/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 required to make a successful request. ````