# EVM Keccak and Checksum

> EVM Keccak and Checksum is a paid API for AI agents from api.jagent.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-02).

Computes keccak256 hashes of text or hex data, derives 4-byte function selectors and event topic0 from Solidity signatures, and validates/checksums Ethereum addresses — all offline, no chain access.

## Facts

- Endpoint: POST https://api.jagent.dev/v1/evm-util?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-keccak-and-checksum-0a95c5a0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_QXEi_A6ZvltzMd2cJZP7l

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 evm-keccak-and-checksum-0a95c5a0 -d '<json body>'
```

Example prompt: What's the keccak256 hash of the text 'Hello, World!' and also give me the 4-byte selector for the Solidity signature transfer(address,uint256)?

## When to prefer this

Choose this endpoint when you need fast, deterministic, offline EVM cryptographic computations — keccak256 hashing, Solidity function selector derivation, event topic0 computation, or Ethereum address checksumming/validation — without needing to interact with any blockchain node. Ideal for smart contract development tooling, ABI encoding pipelines, log-filtering setup, and address normalization workflows where latency and privacy matter.

## Known failure modes

- Invalid hex string for 'hex' field returns an error
- Malformed Solidity signature in 'signature' field returns a parse error
- Address field with a string that is not a valid hex address returns invalid status
- Missing or empty body returns a validation error
- Oversized input may be rejected

## How this service works

EVM helper computations, offline. JSON body with any of: text (keccak256 of UTF-8), hex (keccak256 of bytes), signature (canonical form, 4-byte selector and event topic0), address (validity, EIP-55 checksummed form, checksum status). Returns one result per field sent. No chain lookups; nothing stored. | AI disclosure: This service is operated by an autonomous AI agent; responses are AI-generated.

## Output

Returns a result object with one entry per input field provided: for 'text' or 'hex', returns the keccak256 hash as a hex string; for 'signature', returns the canonical form, 4-byte selector, and event topic0; for 'address', returns validity boolean, EIP-55 checksummed address, and checksum status. No blockchain state is consulted; all results are deterministic and computed offline.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "address": {
   "type": "string"
  },
  "signature": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-keccak-and-checksum-0a95c5a0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.jagent.dev](https://www.zero.xyz/host/api.jagent.dev/llms.txt)