> ## 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. # Simulate a transaction > Simulates an EVM transaction and returns the expected state changes and gas usage. Only supports EIP-155 chains. **Deprecated:** Use the `evaluate-transaction` endpoint instead. ## OpenAPI ````yaml /openapi/client-api.yaml post /clients/me/simulate-transaction 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: 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: 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/simulate-transaction: post: tags: - Deprecated summary: Simulate a transaction description: > Simulates an EVM transaction and returns the expected state changes and gas usage. Only supports EIP-155 chains. **Deprecated:** Use the `evaluate-transaction` endpoint instead. operationId: simulateTransaction parameters: - name: chainId in: query required: true description: > Chain ID in CAIP-2 format (EIP-155 only). For example, `eip155:1` for Ethereum mainnet. schema: type: string requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SimulateTransactionRequest' example: to: '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48' data: 0xa9059cbb000000000000000000000000... value: '0x0' responses: '200': description: Transaction simulated successfully content: application/json: schema: $ref: '#/components/schemas/SimulateTransactionResponse' examples: success: summary: Successful simulation value: changes: - type: transfer from: '0x54968898742c08da211a1cd355447cd1f37f0649' to: '0xdFd8302f44727A6348F702fF7B594f127dE3A902' amount: '10000' token: USDC gasUsed: '65000' error: summary: Simulation error value: error: message: execution reverted '400': description: | Validation error. Common causes: - Missing or invalid chainId - Chain is not EIP-155 - Missing `to` address content: application/json: schema: $ref: '#/components/schemas/SimulateTransactionErrorResponse' example: requestError: message: chainId must be in CAIP-2 format (e.g. eip155:1) '401': description: Unauthorized - invalid or missing authentication token content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' deprecated: true components: schemas: SimulateTransactionRequest: type: object required: - to properties: to: type: string description: The target contract or recipient address. data: type: string description: Encoded transaction data (hex string). value: type: string description: Value to send in wei (hex string). gas: type: string description: Gas limit. gasPrice: type: string description: Gas price in wei. maxFeePerGas: type: string description: Maximum fee per gas (EIP-1559). maxPriorityFeePerGas: type: string description: Maximum priority fee per gas (EIP-1559). SimulateTransactionResponse: type: object properties: changes: type: array items: type: object description: Array of state changes from the simulation. gasUsed: type: string nullable: true description: Amount of gas used by the simulation. error: type: object properties: message: type: string description: Error message if the simulation failed. SimulateTransactionErrorResponse: type: object properties: requestError: type: object properties: message: type: string description: Validation error message. 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. ````