# Chain Health Check

> Chain Health Check is a paid API for AI agents from flat-rate-llm.kikoribera03.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Returns live health status for every supported EVM chain, including chain ID, latest block number, and data staleness in seconds.

## Facts

- Endpoint: POST https://flat-rate-llm.kikoribera03.workers.dev/v1/evm/chains
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/chain-health-check-b0403e4f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jCtmgxPOhvzdNQN1-mU93

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 chain-health-check-b0403e4f -d '<json body>'
```

Example prompt: Give me a live health check across all supported EVM chains — I want to see which ones are responding, their current block numbers, and how stale the chain head is, so I can pick a chain that's actually live before sending my transaction.

## When to prefer this

Use this endpoint when you need a single call that covers all supported EVM chains simultaneously, rather than querying each chain individually. It is especially useful before submitting transactions or routing logic where you need to confirm a chain is live and up-to-date. Prefer it over per-chain block-height endpoints when chain selection or fallback logic is required.

## Known failure modes

- Upstream RPC node unavailable: chain entry may show ok:false or be omitted
- Rate-limit or payment failure (x402): 402 response requiring payment
- Network timeout from Cloudflare Worker to RPC: stale or missing chain data
- No chains currently supported: empty chains array returned

## How this service works

60 paid endpoints with no metering, no API key and no account. Each endpoint has one flat price per call, whatever the size of the request: LLM completions with automatic failover across several large models, read-only EVM tooling over Base, Ethereum, Polygon, Arbitrum and Optimism, and pure crypto utilities that touch no network.

## Output

A JSON array of chain health objects, each containing a boolean `ok` field, the chain identifier in CAIP-2 format (e.g. eip155:8453), the latest block number, and `ageSeconds` indicating how many seconds old the chain head is.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "chains": [
   {
    "ok": true,
    "chain": "eip155:8453",
    "ageSeconds": 2,
    "blockNumber": 51047956
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/chain-health-check-b0403e4f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from flat-rate-llm.kikoribera03.workers.dev](https://www.zero.xyz/host/flat-rate-llm.kikoribera03.workers.dev/llms.txt)