# ChainRead Block Lookup

> ChainRead Block Lookup is a paid API for AI agents from api.firstmention.uk, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-29).

Fetches on-chain block data for a specified block number or 'latest' on Base or Ethereum, paid per-call via x402 USDC micropayment.

## Facts

- Endpoint: POST https://api.firstmention.uk/s/chainread/block?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/chainread-block-lookup-e6b7ead5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__CXK6PRpxAf2rtp602bmW

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 chainread-block-lookup-e6b7ead5 -d '<json body>'
```

Example prompt: Can you fetch block number 19000000 on Ethereum for me so I can see what's in it?

## When to prefer this

Use this endpoint when an AI agent needs to retrieve on-chain block details from Base or Ethereum and can pay $0.01 USDC per call via the x402 micropayment protocol — ideal for agents that need trustless, pay-per-use access without API key management.

## Known failure modes

- Invalid block number format returns an error
- Block number not yet mined returns not-found error
- Unsupported chain value (not 'base' or 'ethereum') returns validation error
- Payment failure via x402 results in 402 response requiring USDC payment on Base
- Network timeout if the RPC node is slow

## How this service works

Pay-per-call HTTP APIs, paid with x402 in USDC on Base (eip155:8453): agentkit, api-change-check, basedue, basewatch, chainread, check-sanctions, chgwatch, company-facts, composite, edgar, feednews, pageaudit, solcheck, token-dd, txpreflight, walletcheck, webmd, webread, websearch, x402index. Each operation describes its service.

## Output

Returns a JSON object with the block data including chain identifier, risk/score fields if applicable, flags, verdict, and metadata about the payer address and price paid in USD.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "hash": {
   "type": "string",
   "description": "0x transaction hash (for /tx)"
  },
  "chain": {
   "enum": [
    "base",
    "ethereum"
   ],
   "type": "string"
  },
  "number": {
   "type": "string",
   "description": "Block number or 'latest' (for /block)"
  },
  "address": {
   "type": "string",
   "description": "0x address or ERC-20 contract address"
  },
  "addresses": {
   "type": "array",
   "items": {
    "type": "string"
   },
   "description": "Up to 25 addresses (for /batch)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "risk": "medium",
  "_meta": {
   "payer": "0x...",
   "price_usd": 0.01
  },
  "chain": "base",
  "flags": [
   {
    "code": "owner_holds_power",
    "severity": "high"
   }
  ],
  "score": 45,
  "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "verdict": "CAUTION"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/chainread-block-lookup-e6b7ead5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.firstmention.uk](https://www.zero.xyz/host/api.firstmention.uk/llms.txt)