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ABI Encode/Decode — EVM Calldata Builder
x402
ABI Encode/Decode — EVM Calldata Builder is a paid API for AI agents from api.agentstools.dev, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).
ABI-encode a Solidity function call (selector + args) or encode/decode arbitrary ABI types to build and parse EVM calldata correctly.
Price / call$0.003
Success—
StatusUnknown
How this service works
ABI-encode a function call (selector + args) or encode/decode arbitrary ABI types — build and parse EVM calldata correctly.
Output
Returns ABI-encoded hex string for encode/encode_call operations, or a structured array of decoded typed values for decode operations. For encode_call, includes the 4-byte function selector prepended to the encoded arguments.
Example use cases
Build calldata for ERC-20 transfer
“Encode a call to the ERC-20 transfer function — signature is transfer(address,uint256) — with recipient 0xDEADBEEF000000000000000000000000DEADBEEF and amount 500000000000000000. Give me the full ABI-encoded calldata.”
Decode unknown transaction calldata
“I have this raw calldata from an on-chain tx: 0xa9059cbb000000000000000000000000deadbeef... — decode it using types [address, uint256] so I can see what arguments were passed.”
Encode arbitrary ABI types for off-chain use
“I need to ABI-encode a (bytes32, uint256, bool) tuple with values ['0xabc...', 42, true] — just encode the types without a function selector.”
Technical details
Endpoint
POSThttps://api.agentstools.dev/crypto/abiWhen to prefer
Use this endpoint when an agent needs to programmatically construct or parse EVM calldata without a local Solidity/ethers.js environment — ideal for serverless agents that need to prepare raw transactions, verify calldata from on-chain events, or serialize arguments for multicall patterns. Prefer over manual encoding when correctness of ABI padding and selector computation is critical.
Side effects
- Invalid function signature format — returns error if signature does not match Solidity ABI syntax
- Mismatched argument count or types — fails if args array length doesn't match the signature's parameter list
- Malformed 0x hex input for decode — error if data is not valid hex-encoded ABI bytes
- Missing required fields (op, signature, types, args) — 400 error for incomplete requests
- Type mismatch — encoding a string where uint256 is expected returns a type coercion error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| op | string | |
| args | array | Argument values for op=encode_call/encode |
| data | string | 0x calldata/abi bytes for op=decode |
| types | array | ABI type list for op=encode/decode |
| signature | string | Function signature for op=encode_call, e.g. transfer(address,uint256) |
Tags
x402
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