# Solidity ABI Calldata Encoder

> Solidity ABI Calldata Encoder is a paid API for AI agents from chain-tools.use.x402atlas.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Encodes canonical typed values into EVM smart-contract ABI calldata, optionally including a 4-byte function selector and exact 256-bit integers.

## Facts

- Endpoint: POST https://chain-tools.use.x402atlas.com/evm/abi-encode
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/solidity-abi-calldata-encoder-6e2b8a44
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-5tDXrM-QGMgg3-Y9wOgy

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 solidity-abi-calldata-encoder-6e2b8a44 -d '<json body>'
```

Example prompt: ABI-encode a call to transfer(address,uint256) on an EVM contract, passing recipient address 0xAbC1234567890abcdef1234567890abcdef123456 and exact uint256 amount 1000000000000000000, and include the 4-byte function selector in the output.

## When to prefer this

Choose this endpoint when you need deterministic, canonical Solidity ABI encoding of typed values for EVM smart-contract calls — especially when you require exact 256-bit integer precision or an optional prepended 4-byte function selector. Prefer it over client-side encoding libraries when operating in a serverless or agent context without a Web3 runtime, or when you need a trusted third-party to produce verifiable calldata. The companion ABI decoder endpoint on the same platform handles the inverse operation.

## Known failure modes

- Invalid or malformed Solidity type string causes encoding error
- Type/value mismatch (e.g. passing a string where uint256 is expected) returns validation error
- Malformed Ethereum address (wrong length or non-hex) rejected
- Integer value exceeds 256-bit range returns overflow error
- Missing required function signature when selector is requested
- Unsupported or non-canonical Solidity type returns type-not-found error

## How this service works

Solidity ABI calldata encoder — encode canonical typed values for an EVM smart-contract function call, with an optional selector and exact 256-bit integers.

## Output

Returns a hex-encoded ABI calldata byte string conforming to the Solidity ABI specification. If a function selector is requested, the output is prefixed with the 4-byte keccak256-derived selector followed by the ABI-encoded parameters. Integers are encoded as exact 256-bit values padded to 32-byte slots.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/solidity-abi-calldata-encoder-6e2b8a44/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from chain-tools.use.x402atlas.com](https://www.zero.xyz/host/chain-tools.use.x402atlas.com/llms.txt)