# Event topic0 from Solidity Event Signature

> Event topic0 from Solidity Event Signature is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-01).

Computes the keccak256 topic0 hash for a given Solidity event signature string

## Facts

- Endpoint: POST https://twin.unykorn.org/abi-event-topic?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/event-topic0-from-solidity-event-signature-105f32e4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bOeWNT5oiCDI87p15sQpa

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 event-topic0-from-solidity-event-signature-105f32e4 -d '<json body>'
```

Example prompt: What is the topic0 hash for the Solidity event signature Transfer(address indexed from, address indexed to, uint256 value)?

## When to prefer this

Use this endpoint when you need to compute the keccak256 topic0 hash for a Solidity event signature to filter or identify EVM event logs, and you want a simple paid API call rather than running a local keccak256 library. Ideal for agents operating in blockchain contexts that need on-demand ABI encoding utilities without a full Ethereum node or local crypto library.

## Known failure modes

- Invalid or malformed Solidity event signature returns an error response
- Missing 'signature' param in request body causes a 400-level error
- Payment failure via x402 protocol prevents execution
- Network timeout on the UnyKorn operator node

## How this service works

Event topic0 from a Solidity event signature — Genesis402 / UnyKorn Operator Network

## Output

Returns a JSON object with ok:true, the type field set to 'abi-event-topic', the computed topic0 keccak256 hex hash for the given event signature, a timestamp, and a payment receipt including transaction hash, USD amount, and receipt ID.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "type": "abi-event-topic",
  "receipt": {
   "tx_hash": "0x<64hex>",
   "amount_usd": 0.001,
   "receipt_id": "g402-<16hex>"
  },
  "generated_at": "<iso8601>"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/event-topic0-from-solidity-event-signature-105f32e4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from twin.unykorn.org](https://www.zero.xyz/host/twin.unykorn.org/llms.txt)