# Web3 Tools Keccak-256 Hash

> Web3 Tools Keccak-256 Hash is a paid API for AI agents from web3-tools.x402tookit.com, paid per call via x402, $0.02/call, status down (last checked 2026-10-23).

Computes the Keccak-256 hash of text or hex bytes, returning the hash, the first 4 bytes (function selector), and NIST SHA3-256 for comparison.

## Facts

- Endpoint: GET https://web3-tools.x402tookit.com/keccak256?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: down
- Last checked: 2026-10-23
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/web3-tools-keccak-256-hash-c4d80fc7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1XU5G7U47C9hCI-d903dQ

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 web3-tools-keccak-256-hash-c4d80fc7
```

Example prompt: Can you compute the Keccak-256 hash of the text 'transfer(address,uint256)' and also show me the first 4-byte selector and the NIST SHA3-256 for comparison?

## When to prefer this

Use this endpoint when you need the Ethereum-flavored Keccak-256 hash specifically (not standard NIST SHA3-256), especially for computing EVM function selectors, event topic hashes, or verifying ABI encoding. Prefer this over general SHA3 tools when the distinction between Keccak-256 and NIST SHA3-256 matters, and when you want both values side-by-side for comparison.

## Known failure modes

- Missing required 'input' query parameter returns an error
- Invalid hex string when encoding=hex causes a parse error
- Empty input may return a hash of empty bytes rather than an error
- Unsupported encoding value (not utf8 or hex) may return a validation error
- Payment failure (x402) prevents the call from completing

## How this service works

Keccak-256 hash (the Ethereum one) of text or hex bytes, with the first-4-byte selector and NIST SHA3-256 for contrast.

## Output

Returns the full 32-byte Keccak-256 hash as a hex string, the first 4 bytes of that hash (useful as an EVM function selector), the NIST SHA3-256 hash of the same input for contrast, the number of input bytes processed, and the encoding used. May also include source/timestamp metadata and disclaimer fields.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "input"
     ],
     "properties": {
      "input": {
       "type": "string",
       "description": "The text, or hex bytes if encoding is hex"
      },
      "encoding": {
       "type": "string",
       "description": "utf8 (default) or hex"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "encoding": {
       "type": [
        "null",
        "string"
       ]
      },
      "sha3_256": {
       "type": [
        "null",
        "string"
       ]
      },
      "keccak256": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "inputBytes": {
       "type": [
        "null",
        "number"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "first4Bytes": {
       "type": [
        "null",
        "string"
       ]
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/web3-tools-keccak-256-hash-c4d80fc7/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from web3-tools.x402tookit.com](https://www.zero.xyz/host/web3-tools.x402tookit.com/llms.txt)