> ## 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. # Create a challenge for contract execution > Generates a challenge for creating a transaction which executes a smart contract. ABI parameters must be passed in the request. To identify the wallet, you must provide either `walletId`, or both `walletAddress` and `blockchain` in the request body. ## OpenAPI ````yaml openapi/user-controlled-wallets.yaml post /v1/w3s/user/transactions/contractExecution openapi: 3.0.3 info: version: '1.0' title: User-Controlled Wallets description: User-Controlled Wallets API documentation. servers: - url: https://api.circle.com security: - BearerAuth: [] tags: - name: Social/ Email Authentication - name: PIN Authentication - name: Users - name: Wallets - name: Transactions - name: Token Lookup - name: Signing paths: /v1/w3s/user/transactions/contractExecution: post: tags: - Transactions summary: Create a challenge for contract execution description: > Generates a challenge for creating a transaction which executes a smart contract. ABI parameters must be passed in the request. To identify the wallet, you must provide either `walletId`, or both `walletAddress` and `blockchain` in the request body. operationId: createUserTransactionContractExecutionChallenge parameters: - $ref: '#/components/parameters/XUserToken' - $ref: '#/components/parameters/XRequestId' requestBody: $ref: >- #/components/requestBodies/CreateContractExecutionTransactionForEndUser responses: '200': content: application/json: schema: $ref: >- #/components/schemas/CreateContractExecutionTransactionForEndUserResponse description: The challenge for the contract execution was successfully created headers: X-Request-Id: $ref: '#/components/headers/XRequestId' '201': content: application/json: schema: $ref: >- #/components/schemas/CreateContractExecutionTransactionForEndUserResponse description: Successfully created a challenge for a contract execution headers: X-Request-Id: $ref: '#/components/headers/XRequestId' '400': $ref: '#/components/responses/DefaultError' '401': $ref: '#/components/responses/NotAuthorized' '404': $ref: '#/components/responses/NotFound' security: - BearerAuth: [] components: parameters: XUserToken: name: X-User-Token description: Unique system generated JWT session token for specific user. required: true in: header schema: type: string XRequestId: name: X-Request-Id in: header description: > Developer-provided identifier for this request, used for tracing requests in Wallets API logs and the Developer Console, and when communicating with Circle Support. **Must be a UUID to appear in logs.** Non-UUID values are accepted by the API but are ignored by logging and tracing systems. schema: $ref: '#/components/schemas/XRequestId' requestBodies: CreateContractExecutionTransactionForEndUser: content: application/json: schema: title: CreateContractExecutionTransactionForEndUserRequest type: object required: - contractAddress - idempotencyKey properties: idempotencyKey: $ref: '#/components/schemas/IdempotencyKey' abiFunctionSignature: $ref: '#/components/schemas/AbiFunctionSignature' abiParameters: $ref: '#/components/schemas/AbiParameters' callData: $ref: '#/components/schemas/CallData' amount: $ref: '#/components/schemas/Amount' contractAddress: $ref: '#/components/schemas/ContractAddress' feeLevel: $ref: '#/components/schemas/FeeLevel' gasLimit: $ref: '#/components/schemas/GasLimit' gasPrice: $ref: '#/components/schemas/GasPrice' maxFee: $ref: '#/components/schemas/MaxFee' priorityFee: $ref: '#/components/schemas/PriorityFee' refId: $ref: '#/components/schemas/TransactionReferenceId' blockchain: $ref: '#/components/schemas/ContractExecutionBlockchain' walletId: $ref: '#/components/schemas/WalletId' walletAddress: $ref: '#/components/schemas/Address' description: Create transaction for end user request required: true schemas: CreateContractExecutionTransactionForEndUserResponse: title: CreateContractExecutionTransactionForEndUserResponse type: object properties: data: type: object required: - challengeId properties: challengeId: $ref: '#/components/schemas/ChallengeId' 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 IdempotencyKey: type: string description: >- Universally unique identifier (UUID v4) idempotency key. This key is utilized to ensure exactly-once execution of mutating requests. To create a UUIDv4 go to [uuidgenerator.net](https://www.uuidgenerator.net). If the same key is reused, it will be treated as the same request and the original response will be returned. example: a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11 format: uuid AbiFunctionSignature: title: AbiFunctionSignature type: string description: "The contract ABI function signature or\_`callData`\_field is required for interacting with the smart contract. The ABI function signature cannot be used simultaneously with\_`callData`. e.g. burn(uint256)" example: burn(uint256) AbiParameters: title: AbiParameters type: array items: anyOf: - type: string - type: integer - type: boolean - type: array items: {} description: "The contract ABI function signature parameters for executing the contract interaction. Supported parameter types include string, integer, boolean, and array. These parameters should be used exclusively with the abiFunctionSignature and cannot be used with\_`callData`." example: - '100' - '1' CallData: title: CallData type: string description: "The raw transaction data, must be an even-length hexadecimal string with the\_`0x`\_prefix, to be executed. It is important to note that the usage of\_`callData`\_is mutually exclusive with the\_`abiFunctionSignature`\_and\_`abiParameters`. Therefore,\_`callData`\_cannot be utilized simultaneously with either\_`abiFunctionSignature`\_or\_`abiParameters`." example: >- 0xcdcd77c000000000000000000000000000000000000000000000000000000000000000450000000000000000000000000000000000000000000000000000000000000001 Amount: title: Amount type: string description: >- The amount of native token that will be sent to the contract abi execution. Optional field for payable api only, if not provided, no native token will be sent. example: '1.0' ContractAddress: title: ContractAddress description: The blockchain address of the contract to be executed. type: string example: '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48' FeeLevel: type: string enum: - LOW - MEDIUM - HIGH example: MEDIUM description: > A dynamic blockchain fee level setting (`LOW`, `MEDIUM`, or `HIGH`) that will be used to pay gas for the transaction. Calculated based on network traffic, supply of validators, and demand for transaction verification. Cannot be used with `gasPrice`, `priorityFee`, or `maxFee`. Estimates for each fee level can be obtained through the [`POST /transactions/transfer/estimateFee`](/api-reference/w3s/developer-controlled-wallets/create-transfer-estimate-fee) API. GasLimit: type: string description: > The maximum units of gas to use for the transaction. Required if `feeLevel` is not provided. Estimates for this limit can be obtained through the [`POST /transactions/transfer/estimateFee`](/api-reference/w3s/developer-controlled-wallets/create-transfer-estimate-fee) API. An insufficient gas limit may cause the transaction to fail on-chain. Use this field with care when manually providing values. GasLimit override (only supported for EOA wallets): Using `gasLimit` together with `feeLevel`, the provided `gasLimit` will override the estimation's gasLimit. example: '21000' GasPrice: type: string description: > For blockchains without EIP-1559 support, the maximum price of gas, in gwei, to use per each unit of gas (see `gasLimit`). Requires `gasLimit`. Cannot be used with `feeLevel`, `priorityFee`, or `maxFee`. Estimates for this fee can be obtained through the [`POST /transactions/transfer/estimateFee`](/api-reference/w3s/developer-controlled-wallets/create-transfer-estimate-fee) API. The wallet service enforces a dynamic minimum `gasPrice` based on current network conditions. Requests specifying a `gasPrice` below this minimum will be rejected MaxFee: type: string example: '5.935224468' description: > For blockchains with EIP-1559 support, the maximum price per unit of gas (see `gasLimit`), in gwei. Requires `priorityFee`, and `gasLimit` to be present. Cannot be used with `feeLevel` or `gasPrice`. Estimates for this fee can be obtained through the [`POST /transactions/transfer/estimateFee`](/api-reference/w3s/developer-controlled-wallets/create-transfer-estimate-fee) API. PriorityFee: type: string example: '1.022783914' description: > For blockchains with EIP-1559 support, the “tip”, in gwei, to add to the base fee as an incentive for validators. Please note that the `maxFee` and `gasLimit` parameters are required alongside the `priorityFee`. The `feeLevel` and `gasPrice` parameters cannot be used with the `priorityFee`. Estimations for this fee can be obtained through the [`POST /transactions/transfer/estimateFee`](/api-reference/w3s/developer-controlled-wallets/create-transfer-estimate-fee) API. The wallet service enforces a dynamic minimum `priorityFee` based on current network conditions. Requests specifying a `priorityFee` below this minimum will be rejected TransactionReferenceId: type: string example: grouptransaction123 description: Optional reference or description used to identify the transaction. ContractExecutionBlockchain: title: ContractExecutionBlockchain type: string description: > Blockchain associated with the contract execution transaction. Required when either of `walletAddress` or `sourceAddress` is provided. The `blockchain` and `walletId` fields are mutually exclusive. enum: - ETH - ETH-SEPOLIA - AVAX - AVAX-FUJI - MATIC - MATIC-AMOY - ARB - ARB-SEPOLIA - UNI - UNI-SEPOLIA - BASE - BASE-SEPOLIA - OP - OP-SEPOLIA - ARC-TESTNET - MONAD - MONAD-TESTNET example: MATIC-AMOY WalletId: title: WalletId type: string format: uuid description: | Unique system generated identifier of the wallet. For contract deploys this wallet ID will be used as the source. example: a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11 Address: title: Address description: > Blockchain generated unique identifier, associated with wallet (account), smart contract or other blockchain objects. type: string example: '0xca9142d0b9804ef5e239d3bc1c7aa0d1c74e7350' ChallengeId: type: string format: uuid description: >- Unique system generated identifier used to initiate a user challenge flow. example: c4d1da72-111e-4d52-bdbf-2e74a2d803d5 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. 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' 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' NotFound: content: application/json: schema: type: object title: NotFoundResponse 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: 404 message: Not found. description: Specified resource was not found. 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. ````