# x402-Testbed Echo Endpoint

> x402-Testbed Echo Endpoint is a paid API for AI agents from health-api.tail11a58f.ts.net, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-31).

Echoes back GET request query parameters for testing x402 payment client integration, with optional 500 error injection before payment settlement.

## Facts

- Endpoint: GET https://health-api.tail11a58f.ts.net/echo?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-testbed-echo-endpoint-6e916561
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0NRyjsp9Qa8iT17bCvaxq

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-testbed-echo-endpoint-6e916561
```

Example prompt: Send a test GET request to the x402 echo endpoint so I can verify my payment client is working correctly — just echo back what was sent, no error injection needed.

## When to prefer this

Choose this endpoint when you need a live, real-money x402 integration test at the lowest possible cost ($0.001 USDC), especially when verifying that your x402 client correctly handles both the happy-path echo response and the pre-payment 5xx error path. Prefer it over mock or sandbox endpoints when you need to confirm end-to-end payment flow with a real facilitator.

## Known failure modes

- expectStatus=500 triggers a 500 Internal Server Error before payment is processed
- Missing or malformed query parameters may result in an empty echo body
- Network timeouts on the Tailscale-hosted endpoint if the host is offline
- x402 payment negotiation failure if client does not support the protocol correctly
- 402 Payment Required returned if payment credentials are absent or invalid

## How this service works

x402 test endpoint (GET) — echo for testing an x402 client with query params only. Returns what it received. Query param expectStatus=500 makes it fail with 500 BEFORE any payment is taken (tests your client error path and proves a 5xx is never treated as paid).

## Output

Returns an echo of the received GET request including query parameters as structured JSON; if expectStatus=500 is supplied, returns an HTTP 500 error response before any payment settlement occurs, allowing the caller to inspect the pre-payment failure path.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "expectStatus": {
       "type": "integer",
       "description": "Set 500 to test post-settlement failure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-testbed-echo-endpoint-6e916561/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from health-api.tail11a58f.ts.net](https://www.zero.xyz/host/health-api.tail11a58f.ts.net/llms.txt)