# EVM Transaction by Block Index

> EVM Transaction by Block Index is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-01).

Retrieves the Nth transaction from a specific block on any of ten supported EVM chains

## Facts

- Endpoint: POST https://twin.unykorn.org/evm-tx-by-index?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evm-transaction-by-block-index-549f968d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qczuMMBh-IMNamDzxB3BO

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-transaction-by-block-index-549f968d -d '<json body>'
```

Example prompt: What's the transaction at index 2 in block 19500000 on Ethereum? Pull the full tx details for that position.

## When to prefer this

Use this endpoint when you need to look up a specific transaction by its ordinal position within a known block, across any of ten major EVM chains (Ethereum, Base, Polygon, Arbitrum, Optimism, BSC, Avalanche, Gnosis, Linea, Scroll). Prefer this over general blockchain explorers when building automated agents that need programmatic, pay-per-use access to positional transaction data without API key management.

## Known failure modes

- Index out of range if the requested transaction index exceeds the number of transactions in the block
- Invalid block identifier if the block hash or number doesn't exist on the specified chain
- Unsupported chain if a chain not in the allowed enum is provided
- Payment failure if the $0.003 USDC x402 payment cannot be processed
- Network timeout if the target chain RPC is slow or unavailable

## How this service works

The Nth transaction in a block — Genesis402 / UnyKorn Operator Network

## Output

Returns a JSON object with ok:true, a type field ('evm-tx-by-index'), a receipt object containing the transaction hash (tx_hash), the USD amount associated with the call (amount_usd), a receipt ID (receipt_id), and a generated_at ISO8601 timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "params": {
   "type": "object",
   "properties": {
    "block": {
     "type": "string"
    },
    "chain": {
     "enum": [
      "ethereum",
      "base",
      "polygon",
      "arbitrum",
      "optimism",
      "bsc",
      "avalanche",
      "gnosis",
      "linea",
      "scroll"
     ],
     "type": "string"
    },
    "index": {
     "type": "integer",
     "minimum": 0
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "type": "evm-tx-by-index",
  "receipt": {
   "tx_hash": "0x<64hex>",
   "amount_usd": 0.003,
   "receipt_id": "g402-<16hex>"
  },
  "generated_at": "<iso8601>"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evm-transaction-by-block-index-549f968d/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)