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Machine Preflight API
x402
Machine Preflight API is a paid API for AI agents from preflight.natio.re, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-11).
Simulates and inspects an unsigned Base (chain ID 8453) transaction for token approvals, privileged selectors, reverts, and smart contract anomalies before signing.
Price / call$0.02
Success—
StatusUnknown
How this service works
Read-only preflight analysis for unsigned Base transactions. Technical signal only; no signing, broadcasting or investment advice.
Output
Returns a JSON report containing a risk level (e.g. 'critical'), a numeric risk score, and an array of findings — each with a code, title, and severity — plus chain metadata (id: 8453, name: 'Base') and a report version string.
Example use cases
DeFi approval safety check
“I'm about to approve a token spend on a DeFi protocol on Base — can you simulate the transaction first and tell me if the approval is unlimited or if anything looks suspicious? My wallet is 0xAaaa...1111, the contract is 0xBbbb...2222, and the calldata is 0x095ea7b3...”
Pre-sign revert detection
“Check whether this Base transaction will revert before I send it — caller is 0xCccc...3333, target is 0xDddd...4444, calldata is 0x23b872dd..., and I'm sending 0 wei. I don't want to waste gas on a failed tx.”
Smart contract anomaly audit
“Can you inspect this unsigned Base mainnet transaction for any privileged selectors or contract code anomalies? The from address is 0xEeee...5555, to is 0xFfff...6666, and the hex calldata is 0x70a08231....”
Technical details
Endpoint
POSThttps://preflight.natio.re/v1/preflight/transaction?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to pre-screen an unsigned Base transaction for security risks before presenting it to a user for signing — especially for DeFi interactions involving token approvals, contract calls with complex calldata, or interactions with unknown or unaudited contracts. It is uniquely suited for wallets, agent-driven transaction flows, and security tooling that must catch unlimited approvals, dangerous privileged selectors, or likely reverts before gas is spent.
Side effects
- Invalid Ethereum address format for 'to' or 'from' returns a validation error
- Non-Base chain ID (anything other than 8453) is rejected in v1
- Malformed or odd-length hex calldata returns a pattern validation error
- Simulated call reverts on-chain resulting in a revert finding in the report
- Oversized calldata exceeding 131074 hex characters rejected
- Network or RPC errors may cause simulation failure with a 5xx response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | Target address of the unsigned transaction. |
| data | string | Hex-encoded calldata, including the four-byte selector. |
| from | string | Required signing address used as the EVM caller for eth_call and gas estimation. |
| chainId | integer | Base mainnet chain ID. Only Base is accepted in v1. |
| valueWei | string | Native value in wei, encoded as an unsigned decimal or hex string. |
Output
Schema · Response
{
"type": "json",
"example": {
"risk": {
"level": "critical",
"score": 60,
"findings": [
{
"code": "UNLIMITED_TOKEN_APPROVAL",
"title": "Effectively unlimited token approval",
"severity": "critical"
}
]
},
"chain": {
"id": 8453,
"name": "Base"
},
"reportVersion": "1.0"
}
}Tags
x402
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