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EVM Transaction Simulation (eth_call Pre-flight)
x402
EVM Transaction Simulation (eth_call Pre-flight) is a paid API for AI agents from x402-audit.tatschluizguilherme.workers.dev, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-13).
Simulates an EVM transaction via eth_call on Base, Optimism, or Ethereum Mainnet before submission, returning success/failure, return data, decoded revert reason, and gas estimate
Price / call$0.1
Success—
StatusUnknown
How this service works
Pay-per-call on-chain API for AI agents and developers: wallet audits, token safety audits (honeypot detection), live gas prices, token prices, transaction receipts, balances, ENS resolution, block data, ERC-20 allowances, transaction simulation, swap quotes and multicall batches — all computed on-chain via public RPCs (no external market API). Pay per request in USDC on Base via the x402 exact scheme (EIP-3009 transferWithAuthorization). No API key, no signup, no subscription.
Output
Returns a success boolean indicating whether the simulated call would succeed, the raw return data from the call, a decoded human-readable revert reason (if the call reverts with Error(string)), and a gas estimate for the transaction — all derived directly from an on-chain eth_call without using any block explorer API.
Example use cases
Pre-flight DeFi swap safety check
“Before I execute this swap on Base, can you simulate it for me? From wallet 0x1234...abcd, to the Uniswap router 0x2626...6868, with calldata 0x...swapExactTokensForTokens, value 0 ETH — I want to know if it'll revert and roughly how much gas it'll use.”
Debug a reverting contract call
“My contract interaction keeps failing on Optimism and I need to know why. Simulate this call from 0xOwner...1111 to contract 0xNFT...2222 with calldata 0x23b872dd...transferFrom, value 0 — can you tell me the decoded revert reason?”
Gas estimation for Ethereum mainnet interaction
“I'm about to call a staking contract on Ethereum mainnet and need a gas estimate before I commit. Simulate the call from 0xMy...wallet to 0xStaking...contract with this calldata 0xa694fc3a...0de0b6b3, value 0.5 ETH — does it succeed and what's the gas?”
Technical details
Endpoint
GEThttps://x402-audit.tatschluizguilherme.workers.dev/simulateWhen to prefer
Choose this endpoint when you need to pre-flight an EVM transaction to check for reverts, decode revert reasons, or estimate gas on Base, Optimism, or Ethereum Mainnet without submitting on-chain. Prefer this over block explorer APIs (Etherscan, etc.) since it performs a live eth_call directly against the node, giving real-time simulation results. Ideal for DeFi agents, smart contract debuggers, or any workflow that must validate transaction safety before committing gas.
Side effects
- Invalid or malformed calldata causes simulation error
- Unsupported chain specified returns an error
- Missing required fields (from/to/data) returns a bad request error
- RPC node timeout or connectivity issue results in a service error
- Value field mismatch with contract requirements causes unexpected revert in simulation
- Custom revert reasons beyond Error(string) (e.g. custom errors) may not be fully decoded
Output
Schema · Response
{
"type": "json",
"example": {
"to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
"from": "0x8e8d53a67b59e6f2a28e0d6d52012a2b0e3e1886",
"network": "base",
"success": true,
"returnData": "0x0000000000000000000000000000000000000000000000000000000000000000",
"blockNumber": 24400123,
"gasEstimate": 30248,
"requestedAt": "2026-08-05T01:30:00.000Z"
}
}Tags
x402
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