# x402 Research Echo

> x402 Research Echo is a paid API for AI agents from x402-echo-service.onrender.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Echoes a submitted message back with its SHA-256 digest and a server timestamp, used for x402 protocol conformance and discovery-layer research.

## Facts

- Endpoint: POST https://x402-echo-service.onrender.com/echo
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-research-echo-c72c0b2d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_unVcF4_wo3g41SERKa7ha

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 x402-research-echo-c72c0b2d -d '<json body>'
```

Example prompt: Echo the message 'hello from agent' through the x402 research echo service and tell me what SHA-256 hash and server timestamp come back.

## When to prefer this

Choose this endpoint when you need to test x402 protocol conformance, probe the x402 discovery layer, or verify SHA-256 hashing behavior in a safe research context where no real payment settlement occurs. It is purpose-built for security research and protocol testing, not for production message hashing or real payment flows.

## Known failure modes

- Empty or missing 'message' field returns a validation error
- Message exceeding 4096 characters is rejected
- Service may be unavailable if the Render.com free-tier instance is sleeping (cold start delay)
- Malformed JSON body returns a parse error
- Network timeout if the instance is spinning up from idle

## How this service works

Echo service for x402 protocol research. POST a JSON body with a "message" string; the response returns the message, its SHA-256 digest and a server timestamp. Payment is live: $0.001 USDC on Base is verified and settled via the Coinbase CDP facilitator, so callers ARE charged. The response is computed before settlement, and the settlement tx hash is returned in the body and in PAYMENT-RESPONSE.

## Output

A JSON object containing three fields: 'echo' (the original message string), 'sha256' (the SHA-256 hex digest of the message), and 'timestamp' (an ISO 8601 UTC datetime string from the server at time of processing). No payment is actually settled despite the x402 payment advertisement.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "message": {
   "type": "string",
   "maxLength": 4096,
   "minLength": 1,
   "description": "Text to echo back."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "echo": "hello world",
  "sha256": "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9",
  "timestamp": "2026-08-18T12:00:00.000Z"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-research-echo-c72c0b2d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-echo-service.onrender.com](https://www.zero.xyz/host/x402-echo-service.onrender.com/llms.txt)