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x402-audit Calldata Decoder
x402
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.
Price / call$0.1
Success—
StatusUnknown
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.
Example use cases
Pre-sign DeFi transaction audit
“I'm about to sign a transaction with calldata '0x23b872dd000000000000000000000000abc...000000000000000000000000def...0000000000000000000000000000000000000000000000008ac7230489e80000' — can you decode it so I know if it's a transferFrom and who the recipient and amount are before I approve it?”
Inspect multicall nested sub-calls
“Decode this multicall calldata for me: '0xac9650d8000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000020000...' — I want to see every individual sub-call it contains and what each one does.”
Verify Gnosis Safe execTransaction
“I received an execTransaction calldata from a Gnosis Safe and I want to know what it's actually going to execute before I add my signature — here's the hex: '0x6a761202...'. Can you decode it and show me the inner call details?”
Technical details
Endpoint
GEThttps://x402-audit.tatschluizguilherme.workers.dev/decode?utm_source=zero.xyzWhen to prefer
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.
Side effects
- 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
Output
Schema · Response
{
"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"
}
}Tags
x402
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