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EVM Transaction Simulator (eth_simulateV1)
x402
EVM Transaction Simulator (eth_simulateV1) is a paid API for AI agents from yonder-spotless-stranger.ngrok-free.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).
Simulates an EVM transaction on Ethereum mainnet or Base and returns revert status, revert reason, gas used, and real token balance deltas for all touched addresses.
Price / call$0.01
Success—
StatusUnknown
How this service works
Pre-flight any EVM transaction and get back whether it reverts, the revert reason, gas used, and the REAL token balance deltas for every address it touches — from an eth_simulateV1 trace, not a gas estimate. Supports Ethereum mainnet and Base. Use it to kill a losing transaction before you pay gas for it.
Output
Returns whether the transaction reverts, the human-readable revert reason if it does, the actual gas consumed, and a list of real token balance deltas (positive or negative) for every address touched by the transaction — derived from a full eth_simulateV1 execution trace, not a static estimate.
Example use cases
DeFi swap safety check
“I'm about to send a Uniswap swap on Ethereum mainnet from 0xSender...111 to the router at 0xRouter...222 with this calldata 0xswapExactTokens... and 0 wei — can you simulate it first and tell me if it'll revert, the gas cost, and which token balances will move?”
Detect failing NFT mint before gas
“Before I mint from this contract at 0xNFT...999 on Base, simulate the call for me — my wallet is 0xMyWallet...456, calldata is 0x1249c58b, value is 10000000000000000 wei — will it succeed or revert, and what does it cost in gas?”
Validate airdrop claim transaction
“I want to claim my airdrop from contract 0xAirdrop...888 on Ethereum mainnet, my address is 0xMe...777 and the calldata is 0xclaim... — simulate the transaction and tell me if it reverts, why, and what my token balance will actually change by.”
Technical details
Endpoint
POSThttps://yonder-spotless-stranger.ngrok-free.dev/simulateWhen to prefer
Use this endpoint when you need to know definitively whether a transaction will revert and why, or when you need accurate token balance deltas across all addresses — not just a gas estimate. Prefer this over eth_estimateGas when revert reasons or actual token flow visibility matters. Ideal before submitting any high-stakes DeFi, NFT, or contract interaction transaction on Ethereum mainnet or Base where wasted gas or unexpected outcomes are costly.
Side effects
- Invalid or malformed address for 'to' or 'from' fields returns a validation error
- Unsupported chain value (not 'mainnet' or 'base') returns an error
- Malformed calldata hex causes simulation failure
- Transaction requires state not available on the node (e.g. future block) may fail or return inaccurate results
- Payment failure (insufficient USDC or x402 protocol error) blocks the call
- Node RPC timeout on complex traces may return an error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | target contract or account |
| data | string | calldata hex, optional |
| from | string | sender address |
| chain | string | mainnet or base |
| value | string | wei, decimal string |
Tags
x402
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