# EVM Transaction Simulation (eth_call Pre-flight)

> 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

## Facts

- Endpoint: GET https://x402-audit.tatschluizguilherme.workers.dev/simulate
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-transaction-simulation-eth-call-pre-flight-87379691
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Q4erT1CI-Beypkujuef0o

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability evm-transaction-simulation-eth-call-pre-flight-87379691
```

Example prompt: Before I submit this transaction, simulate it on Base: from 0xAbC...123, to contract 0xDeF...456, with this calldata 0xa9059cbb000...0001, value 0 ETH — will it succeed, and what's the gas estimate?

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "from": "0x8e8d53a67b59e6f2a28e0d6d52012a2b0e3e1886",
  "network": "base",
  "success": true,
  "returnData": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "blockNumber": 24400123,
  "gasEstimate": 30248,
  "requestedAt": "2026-08-05T01:30:00.000Z"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-transaction-simulation-eth-call-pre-flight-87379691/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-audit.tatschluizguilherme.workers.dev](https://www.zero.xyz/host/x402-audit.tatschluizguilherme.workers.dev/llms.txt)