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Base Calldata Decoder & Pre-Sign Risk Analyzer
x402
Base Calldata Decoder & Pre-Sign Risk Analyzer is a paid API for AI agents from kr-x402-mvp.kgy5612.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).
Decodes raw EVM calldata (or a Base transaction hash) into human-readable function signature, typed arguments, plain-English summary, and a risk verdict before signing.
Price / call$0.002
Success—
StatusUnknown
How this service works
Pay-per-call crypto microdata for trading/onchain AI agents via x402 (USDC on Base): Base gas, token risk, balances, multi-venue prices, Hyperliquid book/funding, kimchi premium. No API keys.
Output
Returns a JSON object containing: the resolved function signature and 4-byte selector, typed and decoded arguments, a plain-English summary of what the transaction does, a risk rating (none/low/medium/high), a verdict string (e.g. CAUTION), an array of risk flags (unlimited_approval, unknown_spender, approve_all_nfts, offchain_permit, permit2_allowance, batched_calls, inner_approval), spender address and label, amount (numeric or 'unlimited'), guidance text, the token/contract label and decimals if a `to` address was provided, and the signature resolution source (builtin, openchain, or 4byte).
Example use cases
Pre-sign approval safety check
“I'm about to sign this calldata on Base: 0x095ea7b3000000000000000000000000000000000022d473030f116ddee9f6b43ac78ba3ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff — the target is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913. Decode it, tell me what it does in plain English, who the spender is, and flag anything risky like unlimited approvals.”
Decode existing Base transaction
“Can you decode Base transaction hash 0xabc123...def456 for me? I want to know what function was called, what the arguments were, and whether there's anything suspicious about it.”
Unknown contract interaction audit
“My wallet is showing a transaction to 0xDeAdBeEf... with calldata 0xa9059cbb... — I don't recognize this contract. Decode the calldata and tell me the risk level before I confirm anything.”
Technical details
Endpoint
GEThttps://kr-x402-mvp.kgy5612.workers.dev/crypto/decode-calldata?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent or wallet needs to explain or risk-assess raw EVM calldata before signing on Base — especially for ERC20 approvals, permit calls, NFT approvals, or any unfamiliar selector. Prefer this over generic block explorers when you need structured, machine-readable output with explicit risk flags suitable for programmatic gating of transaction signing.
Side effects
- Unrecognized 4-byte selector — returns unknown function with no decoded args
- Invalid or malformed calldata hex — 400-level error or partial decode
- Base transaction hash not found or not yet indexed — hash lookup fails
- ABI round-trip collision detected — ambiguous selector flagged
- Contract at `to` address not a token — symbol/decimals lookup returns null
- Calldata too short (less than 4 bytes) — selector cannot be resolved
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"args": [
{
"type": "address",
"value": "0x000000000022D473030F116dDEE9F6B43aC78BA3"
},
{
"type": "uint256",
"value": "115792089237316195423570985008687907853269984665640564039457584007913129639935"
}
],
"risk": "medium",
"chain": "base",
"flags": [
"unlimited_approval"
],
"amount": "unlimited",
"spender": "0x000000000022D473030F116dDEE9F6B43aC78BA3",
"summary": "lets Uniswap Permit2 move ALL USDC from the signer",
"verdict": "CAUTION",
"function": "approve(address,uint256)",
"guidance": "Review the decoded args; simulate with /crypto/base-rpc?method=eth_call before signing.",
"selector": "0x095ea7b3",
"unlimited": true,
"spender_label": "Uniswap Permit2",
"signature_source": "builtin"
}
}Tags
x402
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