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Preflight EVM Transaction Inspector
x402
Preflight EVM Transaction Inspector is a paid API for AI agents from preflight402.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-10-02).
Decodes raw Ethereum or Base transaction bytes or calldata against standard interfaces (ERC-20, ERC-721, ERC-1155, WETH, EIP-2612 Permit, Permit2) and returns the decoded method signature, typed parameters, value in wei, and spec links.
Price / call$0.1
Success—
StatusUnknown
How this service works
Call before signing an Ethereum or Base transaction or calldata. Decodes raw transaction bytes or contract calldata against standard interfaces (ERC-20, ERC-721, ERC-1155, WETH, EIP-2612 Permit and Permit2) in memory. Returns the decoded method signature, typed parameters, value in wei and standard specification links. Mechanical byte decoding only: never simulates state or advises whether to sign.
Output
Returns the decoded method name/signature, typed input parameters with their values, the ETH value in wei attached to the transaction, the matched standard interface (e.g. ERC-20, ERC-721, Permit2), and links to the relevant EIP/standard specification. No state simulation or signing advice is included.
Example use cases
Decode ERC-20 transfer before signing
“I'm about to sign this raw Ethereum calldata — 0xa9059cbb000000000000000000000000ab5801a7d398351b8be11c439e05c5b3259aec9000000000000000000000000000000000000000000000000002386f26fc10000 — can you decode it and tell me the method name, recipient address, and amount?”
Inspect Permit2 approval on Base
“I got a Permit2 signature request on Base with this calldata: 0x2b67b570... — decode it for me before I sign, I want to see the typed parameters and what token and spender it's approving.”
Parse WETH deposit transaction
“What does this raw transaction hex actually do on Ethereum? Here it is: 0xd0e30db0... — I think it's a WETH deposit but I want to see the decoded method signature and value in wei to confirm before I broadcast it.”
Technical details
Endpoint
POSThttps://preflight402.com/v1/evm/tx-inspect?utm_source=zero.xyzWhen to prefer
Use this endpoint when an agent or user needs to understand what a raw Ethereum or Base transaction or calldata is doing before signing it, without executing or simulating it. Ideal for pre-signing safety checks on standard token interactions (ERC-20 transfers, NFT transfers, WETH wraps, permit approvals). Prefer this over full simulation tools when only byte-level decoding is needed and no on-chain state lookup is required.
Side effects
- Calldata does not match any supported interface (ERC-20, ERC-721, ERC-1155, WETH, Permit, Permit2) — returns unrecognized or raw fallback
- Malformed hex input (odd-length or non-hex characters) — returns validation error
- Missing both raw_tx and calldata — returns parameter error
- Unsupported network specified — returns enum validation error
- Payment not received (x402 payment required) — returns 402 Payment Required
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | |
| raw_tx | string | |
| network | string | |
| calldata | string |
Tags
x402
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