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ExactGate x402 Preflight Validator
x402
ExactGate x402 Preflight Validator is a paid API for AI agents from exactgate-x402.insertnameheree.chatgpt.site, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).
Simulates a Base blockchain transaction to estimate gas and determine safety before submission, paid per call via x402 USDC micropayment.
Price / call$0.02
Success—
StatusUnknown
How this service works
Deterministic Base receipt and transaction preflight APIs, paid per call with x402 USDC.
Output
Returns a JSON object with: chainId (8453 for Base), a boolean 'contract' indicating if the target is a contract, 'callResult' (raw hex return data), 'gasEstimate' (estimated gas units as a string), 'safeToSubmit' (boolean safety verdict), and a 'note' confirming no transaction was signed or broadcast.
Example use cases
Pre-flight DeFi swap safety check
“I'm about to call a Uniswap router on Base with from 0xMyWallet...1234, to 0xUniswapRouter...5678, data 0x38ed1739...encoded params, and value 0x0 — can you simulate it and tell me the gas cost and whether it's safe to send?”
Smart contract deployment validation
“Before I deploy this contract bytecode to Base, can you preflight the transaction from 0xDeployer...aaaa to the zero address with data 0x608060405260...bytecode and value 0x0, and confirm the gas estimate and whether it looks safe?”
NFT mint transaction dry-run
“I want to mint an NFT by calling 0xNFTContract...beef on Base from my wallet 0xMyAddress...cafe with calldata 0x6a627842...myaddress and 0.001 ETH (value 0x38D7EA4C68000) — simulate it first and tell me if it'll succeed and how much gas I'll need.”
Technical details
Endpoint
POSThttps://exactgate-x402.insertnameheree.chatgpt.site/v1/base/preflightWhen to prefer
Choose this endpoint when you need a deterministic, no-side-effect dry-run of a Base L2 transaction before committing gas. It is ideal for agent workflows that must validate smart contract interactions, estimate costs, or catch reverts programmatically without risking real funds. Prefer it over generic RPC eth_call wrappers when you want a structured JSON safety verdict (safeToSubmit) rather than raw RPC output, and when you are comfortable paying $0.02 USDC per simulation via x402 micropayment.
Side effects
- Invalid Ethereum address format for 'to' or 'from' returns a 400 validation error
- Malformed or odd-length hex calldata in 'data' is rejected by pattern validation
- Calldata exceeding 8194 hex characters (4097 bytes) is rejected
- Payment failure via x402 protocol results in 402 Payment Required before simulation runs
- Simulated call reverts on-chain returns safeToSubmit: false with revert data in callResult
- Network issues reaching Base RPC may return 503 or timeout errors
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | |
| data | string | |
| from | string | |
| value | string |
Output
Schema · Response
{
"type": "json",
"example": {
"note": "Simulation only; no transaction was signed or broadcast.",
"chainId": 8453,
"contract": true,
"callResult": "0x",
"gasEstimate": "48231",
"safeToSubmit": true
}
}Tags
x402
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