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Calldata Decoder
x402
Calldata Decoder is a paid API for AI agents from bess-x402.onrender.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-30).
Decodes raw EVM transaction calldata by resolving the 4-byte function selector and unpacking all arguments into human-readable form.
Price / call$0.003
Success—
StatusUnknown
How this service works
Decode EVM transaction input data: looks up the 4-byte function selector and decodes every argument (addresses, amounts, arrays). Use to see what a transaction or signing request will really do.
Output
Returns the resolved function name and signature derived from the 4-byte selector, plus each decoded argument with its type and value — including addresses (checksummed), token amounts, booleans, arrays, and nested tuples — giving a complete human-readable breakdown of what the transaction will execute.
Example use cases
Verify a DeFi signing request
“Before I sign this transaction, can you decode the calldata 0x23b872dd000000000000000000000000abc...def000000000000000000000000xyz...123000000000000000000000000000000000000000000000000002386f26fc10000 and tell me exactly what function it's calling and what the arguments are?”
Audit an on-chain transaction
“I found this suspicious transaction on Ethereum with input data 0x38ed1739000000000000000000000000... — can you decode the calldata and show me the function name and every argument so I can understand what it actually did?”
Debug a smart contract interaction
“My smart contract call failed — can you decode this calldata 0x7ff36ab5000000000000000000000000... so I can see what function was called and whether the addresses and amounts were passed in correctly?”
Technical details
Endpoint
GEThttps://bess-x402.onrender.com/v1/evm/decode-calldata?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to understand what an EVM transaction or signing request will actually do before approving or broadcasting it, or when auditing historical on-chain transactions. It is specifically suited for decoding raw hex calldata without needing to supply your own ABI — the endpoint performs the selector lookup automatically. Prefer this over manual ABI decoding tools when working in an automated agent pipeline that needs structured argument output.
Side effects
- Unknown 4-byte selector not in lookup database — function name cannot be resolved
- Malformed or truncated calldata — ABI decoding fails with a parse error
- Non-hex or missing 0x prefix in input — returns validation error
- Empty calldata (e.g. plain ETH transfer with no input) — no function to decode
- ABI ambiguity when multiple functions share the same 4-byte selector
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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