# x402-audit Calldata Decoder

> x402-audit Calldata Decoder is a paid API for AI agents from x402-audit.tatschluizguilherme.workers.dev, paid per call via x402, $0.1/call, status unknown (last checked 2026-10-03).

Decodes raw Ethereum transaction calldata (hex) offline, returning the 4-byte selector, matched function name, typed named arguments, and nested sub-call decoding — no RPC or API key required.

## Facts

- Endpoint: GET https://x402-audit.tatschluizguilherme.workers.dev/decode?utm_source=zero.xyz
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-03
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-audit-calldata-decoder-22286802
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vM3Efa25H3ZLiyaBCaiL8

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 x402-audit-calldata-decoder-22286802
```

Example prompt: Before I sign this transaction, can you decode the calldata '0xa9059cbb000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa9604500000000000000000000000000000000000000000000000de0b6b3a7640000' and tell me exactly what function it calls and with what arguments?

## When to prefer this

Prefer this endpoint when you need instant, offline ABI decoding of raw calldata without requiring an RPC node, blockchain explorer, or API key. Ideal for pre-signing audits, relayer pipelines, or any agent that needs to understand what a transaction does before executing or approving it. Best for the ~40 common DeFi functions (ERC-20, Uniswap, Aave, Gnosis Safe, etc.); for exotic or custom contract ABIs not in the dictionary, a full ABI-aware decoder would be needed.

## Known failure modes

- Unknown selector not in ~40-function dictionary returns selector only with no function match
- Malformed or truncated hex calldata causes decoding error
- Non-hex or empty input returns validation error
- Deeply nested or non-standard ABI encodings may not fully decode inner payloads
- Payment failure ($0.10 USDC x402) blocks request before decoding

## How this service works

Pay-per-call on-chain API for AI agents and developers: wallet audits, token safety audits (honeypot detection), live gas prices, token prices, transaction receipts, balances, ENS resolution, block data, ERC-20 allowances, transaction simulation, swap quotes and multicall batches — all computed on-chain via public RPCs (no external market API). Pay per request in USDC on Base via the x402 exact scheme (EIP-3009 transferWithAuthorization). No API key, no signup, no subscription.

## Output

Returns a JSON object containing the 4-byte function selector, the matched function name from the built-in dictionary (e.g. transfer, approve, swap, multicall), fully typed and named decoded arguments with their values, and where applicable, recursively decoded nested sub-calls (e.g. inner calls within multicall bytes[] arrays or Gnosis Safe execute payloads). Runs entirely offline with no blockchain RPC calls.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": "0xa9059cbb000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA9604500000000000000000000000000000000000000000000000000000000000f4240",
  "network": "offline",
  "function": {
   "args": [
    "0xd8da6bf26964af9d7eed9e03e53415d37aa96045",
    "1000000"
   ],
   "name": "transfer",
   "known": true,
   "nested": null,
   "selector": "0xa9059cbb",
   "argsNamed": {
    "to": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045",
    "value": "1000000"
   },
   "signature": "transfer(address,uint256)",
   "decodeError": false
  },
  "selector": "0xa9059cbb",
  "inputSize": 68,
  "requestedAt": "2026-08-05T08:00:00.000Z"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-audit-calldata-decoder-22286802/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-audit.tatschluizguilherme.workers.dev](https://www.zero.xyz/host/x402-audit.tatschluizguilherme.workers.dev/llms.txt)