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NodeFlare Transaction Simulation API
x402
NodeFlare Transaction Simulation API is a paid API for AI agents from rpc.nodeflare.app, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-13).
Simulates an EVM transaction before sending to determine if it will revert, estimate gas, and identify token/ETH balance changes.
Price / call$0.002
Success—
StatusUnknown
How this service works
Transaction pre-flight: will it revert (and why), gas, and which tokens/ETH move - before you send. Built for agents.
Output
Returns whether the transaction will succeed or revert (with a decoded revert reason if applicable), a gas estimate, and a breakdown of all ERC-20 token transfers and ETH movements that would occur if the transaction were submitted.
Example use cases
DeFi swap safety check
“I'm about to do a Uniswap swap on Ethereum from my wallet 0xabc123, calling the router at 0xdef456 with this calldata. Can you simulate it first to confirm it won't revert, give me a gas estimate, and show me exactly how much ETH and tokens will change hands?”
Debug a failing contract call
“My transaction to this NFT contract keeps failing — the contract is at 0x789abc on Arbitrum and here's the calldata. Can you simulate it and tell me the revert reason so I know what's going wrong?”
Token approval and transfer preview
“Before I sign this transaction to deposit into a yield vault at 0x456def on Base, simulate it for me so I can see the exact token amounts that will leave my wallet and confirm there's no unexpected behavior.”
Technical details
Endpoint
POSThttps://rpc.nodeflare.app/data/simulate/x402?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to pre-validate an EVM transaction before signing and broadcasting — especially in agentic workflows where sending a failing transaction would waste gas or cause irreversible state changes. Ideal when you need both the revert prediction AND token flow analysis in a single call, rather than running a separate eth_call plus token event trace. Particularly useful for DeFi interactions, contract debugging, and any agent that must confirm transaction safety before user approval.
Side effects
- Invalid or malformed transaction object returns a 400 error
- Unsupported chain ID returns an error indicating the chain is not available
- Node timeout or RPC error may return a 503 or gateway error
- Insufficient calldata may produce an incomplete simulation result
- Contract at target address may not be deployed on specified chain
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | |
| data | string | |
| from | string | |
| block | string | |
| chain | string | |
| value | string |
Tags
x402
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