x402 Format Checker

com.crewofthecaptainPublished by crewofthecaptain.comOfficial publisherv1.3.0Updated Oct 24, 2026

IBAN, EU VAT, NIP, REGON, PESEL, email checks. Only $0.001 (0.1 cent) per check via x402 on Base

VerifiedStreamable HTTPWeb executableFinanceBusiness & Commerce

Overview

AI-generated overview

A remote MCP server that validates IBAN, EU VAT, Polish NIP/REGON/PESEL and email formats, charging a small per-check fee in USDC via x402.

What you can do
List the available checks, price, network and payment details for free, then run paid validations one at a time. Validate IBANs with country length and mod-97 checksum, and EU VAT numbers by per-country format (offline, no VIES). Validate Polish identifiers: NIP, REGON and PESEL, including PESEL's encoded birth date and sex. Validate email address syntax without DNS lookups. Each check returns type, valid, normalized and reason, with the input not echoed or stored and personal identifiers masked.
When to use it
Useful when an assistant needs to check whether bank account, tax or personal identifier numbers and email addresses are well-formed, for example while cleaning up business records or onboarding data. The free listing tool lets you inspect pricing before committing.
Requirements
A remote streamable HTTP endpoint; no local runtime, account, API key or headers are declared. Each validation is paid per check via x402 in USDC on Base, so a funded wallet and x402-capable client are needed. Network access to the endpoint is required.
Before you install
Every validation call costs $0.001 in USDC on Base, so repeated checks spend real money; use the free listing tool first. The identifiers sent are personal or business data (IBAN, tax IDs, PESEL, email) and are transmitted to a third-party service, even though it states inputs are not stored and are masked.

Installation

In SourceWeft

  1. Open x402 Format Checker in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/com.crewofthecaptain%2Fformat-checker/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "x402-format-checker": {
      "type": "http",
      "url": "https://validate.crewofthecaptain.com/mcp"
    }
  }
}

Tools

7

list_types

List the available checks, price, network and payment details (free). Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

Takes no parameters.

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

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. Returns {type, valid, normalized, reason}; the input is never echoed or stored and personal identifiers are masked.

Parametersvaluerequired

Version history

2
  1. v1.3.0LatestOct 11, 2026
  2. v1.2.0Oct 11, 2026

Score

72% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts

    Publish an icon in the registry entry.

  • Documentation15 pts

    Declare a GitHub repository with a README, or serve resource_documentation in the OAuth protected-resource metadata.

  • LicenseNot applicable

    A hosted service is used under its provider's terms, so no license is expected here. This check is left out of the percentage.