> ## Documentation Index > Fetch the complete documentation index at: https://docs.portalhq.io/llms.txt > Use this file to discover all available pages before exploring further. # Build a user operation > Builds an ERC-4337 user operation (EntryPoint v0.6) for an Account Abstraction client from one or more calls, which the smart account executes in order. Returns the user operation and the hash to sign. Sign `userOpHash` with the Enclave MPC API `POST /v1/raw/sign/SECP256K1` (or `rawSign` in the SDKs), then submit both with `broadcast-user-operation`. Gas is sponsored when the environment has gas sponsorship configured for the chain; otherwise `paymasterAndData` is `0x` and the smart account pays for gas. The environment's transaction policies are evaluated on every call. ## OpenAPI ````yaml /openapi/client-api.yaml post /clients/me/chains/{chain}/assets/send/build-user-operation openapi: 3.1.0 info: title: Portal Client API version: '3.0' description: > The Portal Client API provides endpoints for managing wallets, building transactions, and interacting with blockchain networks. All endpoints require authentication via a Client API Key or Client Session Token (CST) passed as a Bearer token. ## Base URL `https://api.portalhq.io/api/v3` ## Authentication Include your Client API Key or Client Session Token as a Bearer token in the `Authorization` header of every request. ## Chain ID Format Chain parameters use either friendly names (e.g. `ethereum`, `solana`) or CAIP-2 format (e.g. `eip155:1`, `solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp`). When using CAIP-2 format in URLs, ensure the colon is URI-encoded (`%3A`). servers: - url: https://api.portalhq.io/api/v3 description: Production security: - bearerAuth: [] tags: - name: Clients description: Core client management endpoints - name: Wallet description: >- Read wallet state — balances, NFTs, transaction history, capabilities, and transaction details - name: Transactions description: Build, broadcast, and evaluate blockchain transactions - name: Funding description: Fund wallets with testnet tokens - name: Wallet Shares description: Manage signing and backup share pairs - name: Delegations description: Manage token approvals, revocations, and delegated transfers - name: Session Keys description: Manage EIP-7702 session keys for smart accounts - name: 0x description: Token swap endpoints powered by the 0x protocol - name: Yield.xyz description: Yield opportunities and staking actions powered by Yield.xyz - name: Yield.xyz Borrow description: >- Supply collateral, borrow, repay and withdraw from lending markets (Aave V3, Morpho Blue, SparkLend, Lista) powered by Yield.xyz Borrow - name: Yield.xyz Perps description: >- Trade perpetual futures — open/close leveraged positions, manage stop-loss/take-profit, and fund/withdraw a trading account — powered by Yield.xyz Perps - name: Li.Fi description: Cross-chain swaps and bridging powered by Li.Fi - name: Blockaid description: Transaction and address security scanning powered by Blockaid - name: Hypernative description: >- Transaction, address, token, and NFT security scanning powered by Hypernative - name: Noah description: KYC onboarding, payins, and payouts powered by Noah - name: Meld description: Buy and sell crypto with fiat through aggregated providers powered by Meld - name: Due description: Payins, payouts, virtual accounts, and FX powered by Due - name: EIP-7702 description: EIP-7702 account type detection and authorization management - name: Deprecated description: >- Legacy endpoints scheduled for removal. Use the newer equivalents listed in each endpoint's description. paths: /clients/me/chains/{chain}/assets/send/build-user-operation: post: tags: - Transactions summary: Build a user operation description: > Builds an ERC-4337 user operation (EntryPoint v0.6) for an Account Abstraction client from one or more calls, which the smart account executes in order. Returns the user operation and the hash to sign. Sign `userOpHash` with the Enclave MPC API `POST /v1/raw/sign/SECP256K1` (or `rawSign` in the SDKs), then submit both with `broadcast-user-operation`. Gas is sponsored when the environment has gas sponsorship configured for the chain; otherwise `paymasterAndData` is `0x` and the smart account pays for gas. The environment's transaction policies are evaluated on every call. operationId: buildUserOperation parameters: - $ref: '#/components/parameters/chain' requestBody: required: true content: application/json: schema: type: object required: - calls properties: calls: type: array minItems: 1 description: The calls the smart account makes, in order. items: type: object required: - to properties: to: type: string description: The address to call. value: type: string description: >- Native value in wei, as a decimal or hex string. Defaults to `0`. data: type: string description: Hex calldata. Defaults to `0x`. example: calls: - to: '0xd2b58253741d22bc530b214f8fe81bf1a78a72b1' value: '0' - to: '0x9533731C8224CEc3E53D76B72b590D347d9257eC' value: '0' data: 0x responses: '200': description: User operation built content: application/json: schema: type: object properties: data: type: object properties: userOperation: type: string description: >- The user operation as a JSON string. Pass it unchanged to `broadcast-user-operation`. userOpHash: type: string description: The user operation hash to sign. metadata: type: object properties: chainId: type: string totalGas: type: string description: >- Gas units the user operation is bounded by (sum of its gas limits), as a decimal string. maxFeePerGas: type: string description: >- Maximum price per gas unit in wei, as a decimal string. estimatedGasCostWei: type: string description: >- `totalGas` times `maxFeePerGas`: the most the user operation can cost in wei when the smart account pays for gas. example: data: userOperation: >- {"sender":"0xF86e3fAe8443e4494a689fcDd4C8e6C76c1b2C96","nonce":"0x5","initCode":"0x","callData":"0x34fcd5be...","paymasterAndData":"0x","signature":"0x00000000ffff...","maxFeePerGas":"0x58556415","maxPriorityFeePerGas":"0x15d0ea4","callGasLimit":"0x3f9b","verificationGasLimit":"0x13d75","preVerificationGas":"0xc808"} userOpHash: >- 0xba1f6f1fe76b7a39d660bd02f54a3de5eae99ab413a95246e394c06786003847 metadata: chainId: eip155:11155111 totalGas: '148760' maxFeePerGas: '1481991189' estimatedGasCostWei: '220461009275640' '400': description: > Bad request. Common causes: - The client does not have Account Abstraction enabled - `calls` is missing or empty, or a call has an invalid `to`, `value` or `data` - The chain is not an EVM chain content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: error: >- Account Abstraction is not enabled, contact support to enable it '401': description: Unauthorized - invalid or missing authentication token content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '403': description: A transaction policy blocked one of the calls. content: application/json: schema: type: object properties: error: type: string policyViolation: type: object properties: policyId: type: string policyName: type: string reason: type: string ruleId: type: string example: error: 'Policy violation: amount exceeds limit (Max transfer)' policyViolation: policyId: policyId policyName: Max transfer reason: amount exceeds limit (Max transfer) ruleId: ruleId components: parameters: chain: name: chain in: path required: true description: > The blockchain chain identifier. Use either a friendly name or CAIP-2 format. When using CAIP-2 format in URLs, ensure the colon (`:`) is URI-encoded as `%3A`. **Supported chains:** - `ethereum` (`eip155:1`) - `sepolia` (`eip155:11155111`) - `base` (`eip155:8453`) - `base-sepolia` (`eip155:84532`) - `polygon` (`eip155:137`) - `polygon-mumbai` (`eip155:80001`) - `celo` (`eip155:42220`) - `celo-alfajores` (`eip155:44787`) - `monad` (`eip155:143`) - `monad-testnet` (`eip155:10143`) - `solana` (`solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp`) - `solana-devnet` (`solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1`) - `tron` (`tron:mainnet`) - `tron-nile` (`tron:nile`) - `tron-shasta` (`tron:shasta`) - `stellar` (`stellar:pubnet`) - `stellar-testnet` (`stellar:testnet`) - `bitcoin-segwit` (`bip122:000000000019d6689c085ae165831e93-p2wpkh`) - `bitcoin-segwit-testnet` (`bip122:000000000933ea01ad0ee984209779ba-p2wpkh`) - `bitcoin-p2wpkh` (`bip122:000000000019d6689c085ae165831e93-p2wpkh`) - `bitcoin-p2wpkh-testnet` (`bip122:000000000933ea01ad0ee984209779ba-p2wpkh`) schema: type: string examples: ethereum: value: ethereum summary: Ethereum mainnet (friendly name) eip155: value: eip155:1 summary: Ethereum mainnet (CAIP-2) solana: value: solana summary: Solana mainnet (friendly name) bitcoin: value: bitcoin-segwit summary: Bitcoin segwit (friendly name) schemas: ErrorResponse: type: object properties: error: type: string description: Error message describing what went wrong securitySchemes: bearerAuth: type: http scheme: bearer description: > Client API Key or Client Session Token (CST). Pass as a Bearer token in the Authorization header. ````