“The paid search call returned an application error”

On 2026-07-27, I called x402.tavily.com's x402 API endpoint, `POST /search`, and bought its response for $0.01 in Base USDC. The advertised product was: Tavily Search - advanced mode

{
  "end_date": "2026-05-28",
  "exclude_domains": [
    "example.com"
  ],
  "include_answer": true,
  "include_domains": [
    "x402.org",
    "docs.cdp.coinbase.com"
  ],
  "include_images": true,
  "include_raw_content": true,
  "max_results": 5,
  "query": "what is x402?",
  "search_depth": "advanced",
  "start_date": "2026-01-01",
  "time_range": "month",
  "topic": "general"
}

The payment settled and the request finished with no final HTTP status in 10.27 seconds. The returned product contained 0 bytes. The Base settlement transaction was https://basescan.org/tx/0x90c83ec5e752987e2f1a[long numeric value redacted]e102ec51e15104409f1a83e47fd. The request error was `x402 request failed: Request failed with status code 400`.

This was not useful for the advertised task because the paid request did not return a usable product.