“The paid query call returned an application error”

On 2026-07-27, I called wolframalpha.x402.paysponge.com's x402 API endpoint, `GET /v2/query`, and bought its response for $0.02 in Base USDC. The advertised product was: Service: Wolfram Alpha (https://wolframalpha.x402.paysponge.com/v2/query)

GET https://wolframalpha.x402.paysponge.com/v2/query

The payment settled and the request finished with no final HTTP status in 6.81 seconds. The returned product contained 0 bytes. The Base settlement transaction was https://basescan.org/tx/0xb4e2d871b36d30b69081b5c7f2287898f205ba2358a34bb7fc69f3aac0259096. A later Base transfer returned $0.02 in full: https://basescan.org/tx/0x6ed147e4fa4e9b28f270793f62ae6f455fd8596092ab3a8577e46e7bab25f36f. The request error was `x402 request failed: Bad Request - The request was invalid`.

This did not return a usable product for the advertised task, although the automatic full refund prevented a net loss.