# Base Block Header Lookup

> Base Block Header Lookup is a paid API for AI agents from x402.agentindex.world, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-10).

Fetch a Base mainnet block header and transaction hashes by block number, tag (latest/earliest/safe/finalized), or block hash.

## Facts

- Endpoint: GET https://x402.agentindex.world/base/block?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-block-header-lookup-40e2e307
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_rou4OcTQIMGm8NQjC2vPw

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 base-block-header-lookup-40e2e307
```

Example prompt: Can you fetch the latest block on Base mainnet and give me the block number, timestamp, and the list of transaction hashes in it?

## When to prefer this

Choose this endpoint when you need lightweight block-level metadata and transaction hash lists from Base mainnet without setting up your own RPC node or paying for a full node provider subscription. Ideal for agents that need to confirm block finality, extract transaction hashes for downstream lookups, or monitor chain progress on Base. Not suitable if you need full transaction objects (receipts, logs, decoded calldata) — those require separate calls.

## Known failure modes

- Block not found — if a block number or hash does not exist on Base mainnet, returns null or an error
- Invalid hash format — malformed block hash string results in an RPC error
- Future block number — requesting a block number beyond the current chain tip returns null
- Missing parameters — if neither hash nor number is provided, behavior defaults to latest or may return an error
- Network/RPC timeout — occasional latency spikes from the underlying Base node

## How this service works

Fetch a Base mainnet block header and transaction hashes by number, tag (latest/earliest/safe/finalized), or hash via eth_getBlockByNumber/eth_getBlockByHash.

## Output

Returns a block header object for the requested Base mainnet block, including block number, hash, parent hash, timestamp, miner/coinbase address, gas used, gas limit, and an array of transaction hashes contained in the block.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hash": {
   "anyOf": [
    {
     "type": "string"
    },
    {
     "type": "null"
    }
   ],
   "title": "Hash",
   "default": null
  },
  "number": {
   "anyOf": [
    {},
    {
     "type": "null"
    }
   ],
   "title": "Number",
   "default": null
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-block-header-lookup-40e2e307/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.agentindex.world](https://www.zero.xyz/host/x402.agentindex.world/llms.txt)