# Block Hash at a Given Bitcoin Height

> Block Hash at a Given Bitcoin Height is a paid API for AI agents from twin.unykorn.org, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-29).

Returns the block hash for a specified Bitcoin block height

## Facts

- Endpoint: POST https://twin.unykorn.org/btc-block-at-height?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/block-hash-at-a-given-bitcoin-height-e5f94ed8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iiWmvt-XjhajgOldYaV-U

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 block-hash-at-a-given-bitcoin-height-e5f94ed8 -d '<json body>'
```

Example prompt: What's the Bitcoin block hash at height 840000?

## When to prefer this

Use this endpoint when you need to resolve a specific Bitcoin block height to its canonical block hash, particularly in blockchain auditing, timestamp verification, or cross-chain reference scenarios. Prefer this over manual RPC calls when you need a simple pay-per-call REST interface without running your own Bitcoin node.

## Known failure modes

- Invalid or negative height value — returns an error response
- Height exceeds current chain tip — block does not yet exist
- Network or upstream Bitcoin node unavailability — may return a 5xx or error payload
- Payment failure — x402 payment not accepted, request not processed

## How this service works

Block hash at a given Bitcoin height — Genesis402 / UnyKorn Operator Network

## Output

Returns a JSON object with a boolean ok field, an endpoint type identifier, the block hash at the requested height, a payment receipt (including transaction hash, USD amount, and receipt ID), and a generated_at ISO8601 timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "params": {
   "type": "object",
   "properties": {
    "height": {
     "type": "integer",
     "minimum": 0
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "type": "btc-block-at-height",
  "receipt": {
   "tx_hash": "0x<64hex>",
   "amount_usd": 0.25,
   "receipt_id": "g402-<16hex>"
  },
  "generated_at": "<iso8601>"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/block-hash-at-a-given-bitcoin-height-e5f94ed8/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)