# Preflight EVM Transaction Inspector

> 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.

## Facts

- Endpoint: POST https://preflight402.com/v1/evm/tx-inspect?utm_source=zero.xyz
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/preflight-evm-transaction-inspector-0d948800
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UP54_LoArQVpulM6_l5uv

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability preflight-evm-transaction-inspector-0d948800 -d '<json body>'
```

Example prompt: Before I sign this Ethereum transaction, decode the raw calldata for me — it starts with 0xa9059cbb... — and tell me what method is being called, the recipient address, and the token amount in wei.

## When to prefer this

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.

## Known failure modes

- 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

## 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.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string",
   "pattern": "^0x[0-9a-fA-F]{40}$"
  },
  "raw_tx": {
   "type": "string",
   "pattern": "^0x([0-9a-fA-F]{2})*$"
  },
  "network": {
   "enum": [
    "ethereum",
    "base"
   ],
   "type": "string"
  },
  "calldata": {
   "type": "string",
   "pattern": "^0x([0-9a-fA-F]{2})*$"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/preflight-evm-transaction-inspector-0d948800/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from preflight402.com](https://www.zero.xyz/host/preflight402.com/llms.txt)