# Plainchain x402 Echo

> Plainchain x402 Echo is a paid API for AI agents from plainchain.appin60.com, paid per call via x402, $0.001042/call, status unknown (last checked 2026-10-14).

Echoes back a verified x402 payment receipt, confirming that a micropayment was correctly received, parsed, and validated before granting access to Plainchain's blockchain data APIs.

## Facts

- Endpoint: GET https://plainchain.appin60.com/v1/x402/echo?utm_source=zero.xyz
- Price: $0.001042/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/plainchain-x402-echo-faed52c9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_n5vegCeDk9f1RxHR-drC3

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 plainchain-x402-echo-faed52c9
```

Example prompt: Can you verify my x402 payment receipt on Plainchain — I want to confirm my PAYMENT-SIGNATURE header was accepted and the $0.001042 USDC authorization on Base was parsed correctly before I start querying blockchain data?

## When to prefer this

Use this endpoint when you need to validate that your x402 micropayment integration is correctly configured before calling Plainchain's substantive blockchain data endpoints. It is the right choice for debugging payment flows, confirming payer address extraction, verifying extension handling (e.g. bazaar), or testing that USDC authorization amounts are parsed correctly on Base — all without consuming a higher-cost data query.

## Known failure modes

- Missing or malformed PAYMENT-SIGNATURE header returns a 402 Payment Required response
- Insufficient payment amount causes authorization failure
- Wrong network specified in payment header causes rejection
- Invalid x402 version in header may not be parsed
- Expired payment authorization window causes failure

## How this service works

Gas, balances, token data, address type, approvals, transaction decoding, x402 receipt verification and verifiable randomness on Base, Arbitrum, Ethereum and Optimism. No API key: pay $0.001-$0.01 per call in USDC on Base via x402.

## Output

Returns a JSON object containing: the payer's wallet address, the payment scheme (e.g. 'exact'), the network identifier (e.g. 'eip155:8453' for Base), x402 protocol version, the authorized amount in micro-USDC, the list of echoed extensions (e.g. ['bazaar']), and header check results including whether the bazaar extension was echoed and the expected header name.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "required": {
   "type": "string"
  },
  "properties": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "payer": "0x...",
  "advice": [],
  "checks": {
   "headerName": "PAYMENT-SIGNATURE (v2)",
   "bazaarExtensionEchoed": true
  },
  "scheme": "exact",
  "network": "eip155:8453",
  "x402Version": 2,
  "amountAuthorized": "1042",
  "extensionsEchoed": [
   "bazaar"
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/plainchain-x402-echo-faed52c9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from plainchain.appin60.com](https://www.zero.xyz/host/plainchain.appin60.com/llms.txt)