Discover / x402-test.crewofthecaptain.com

x402 Format Checker

■ Challenge detected

Format and checksum validation for IBAN, EU VAT, Polish NIP/REGON/PESEL and email, pay-per-call via x402. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base. POST JSON {"value": "..."}; values are never stored and personal identifiers are masked. Also a remote MCP server (/mcp) and A2A agent (/.well-known/agent-card.json).

Listed price
$0.001
Challenge detected
3 of the last 3 checks
Median response
443 ms
Last checked
16 Oct, 23:40 UTC
In our index since
14 Oct 2026

Endpoint

curl -i https://x402-test.crewofthecaptain.com/api/validate/email
# 402 Payment Required: pay with an x402 client (USDC on Base),
# then send the same request again with the payment attached.
6 listed endpoints · on x402-list.com

Checks and payment terms on this page refer to the endpoint above. Other listed endpoints have not been checked individually.

Base URLhttps://x402-test.crewofthecaptain.com/api/validate

  • GET/iban$0.001IBAN: country length + ISO 13616 mod-97 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base
  • GET/email$0.001Email address syntax (dot-atom local part, LDH domain; no DNS). Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base
  • GET/pl-pesel$0.001Polish PESEL: checksum + encoded birth date and sex. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base
  • GET/pl-nip$0.001Polish NIP tax id: 10 digits + weighted mod-11 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base
  • GET/pl-regon$0.001Polish REGON: 9 or 14 digits + mod-11 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base
  • GET/eu-vat$0.001EU VAT number: per-country format (offline, no VIES); PL also NIP checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base

A dash means the listing gives no price or method. Copy buttons copy the full URL.

Showing 6 of 6 listed endpoints.

Agents can find it through the Superstables MCP server and JSON API: GET /api/v1/services/x402-test.crewofthecaptain.com

Recent checks

14 Oct 2026One bar per check, showing up to 20 recent checks. Coloured bars show relative response time, with a minimum visible height; full-height grey bars mean no challenge was detected. “Challenge detected” means HTTP 402 or another detected payment-challenge signal.16 Oct 2026
All 3 checks
When (UTC)ResultHTTPResponse
16 Oct, 23:40 UTCChallenge detected402325ms
15 Oct, 19:10 UTCChallenge detected402443ms
14 Oct, 12:00 UTCChallenge detected402465ms

Questions

Did our last probe detect a payment challenge?

At our last probe on 16 Oct, 23:40 UTC, it returned HTTP 402 or another detected payment-challenge signal. This check did not test payment, delivery or compatibility with the Superstables client.

What price is recorded for x402 Format Checker?

Its listed price is $0.001.

What payment terms does x402 Format Checker advertise?

The listing advertises x402, Base and USDC. Check the seller's current payment challenge and authentication requirements before paying.

Where is x402 Format Checker listed?

In x402-list.com. Superstables first indexed it on 14 Oct 2026.

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