# CheckDigit (remote · checkdigit.mike-tusa.workers.dev)

Offline check-digit validation for IBAN, BIC, EU VAT, GTIN/EAN/UPC and ISBN. Format check only.

- Trust score: 72/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-10-24

## Components

- remote · `checkdigit.mike-tusa.workers.dev`: 72/100 (this document), [markdown](https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit.md), [page](https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit)

## Channel facts

- Endpoint: `https://checkdigit.mike-tusa.workers.dev/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.2.1`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-10-24.

- **Endpoint Security**: 69/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - No authorisation is required to call this server. Every tool declares its destructiveHint and none is destructive, so open access doesn't expose one.
  - HTTPS enforcement could not be verified: the plaintext port answered with HTTP 405, which proves neither a plaintext path nor enforcement.
  - The HSTS (Strict-Transport-Security) header is present.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 68/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 501 tokens (~250/item across 2 items; 2 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 30/100
  - Stability observed for 9 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 2 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 3 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the CheckDigit MCP server?

CheckDigit is a hosted endpoint at https://checkdigit.mike-tusa.workers.dev/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http dev-workers-mike-tusa-checkdigit-checkdigit 'https://checkdigit.mike-tusa.workers.dev/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "dev-workers-mike-tusa-checkdigit-checkdigit": {
      "url": "https://checkdigit.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "dev-workers-mike-tusa-checkdigit-checkdigit": {
      "type": "http",
      "url": "https://checkdigit.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.dev-workers-mike-tusa-checkdigit-checkdigit]
url = "https://checkdigit.mike-tusa.workers.dev/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "dev-workers-mike-tusa-checkdigit-checkdigit": {
      "type": "remote",
      "url": "https://checkdigit.mike-tusa.workers.dev/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add dev-workers-mike-tusa-checkdigit-checkdigit --url 'https://checkdigit.mike-tusa.workers.dev/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  dev-workers-mike-tusa-checkdigit-checkdigit:
    url: "https://checkdigit.mike-tusa.workers.dev/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "dev-workers-mike-tusa-checkdigit-checkdigit": {
      "Transport": "http",
      "Url": "https://checkdigit.mike-tusa.workers.dev/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add dev-workers-mike-tusa-checkdigit-checkdigit -t streamable-http -u 'https://checkdigit.mike-tusa.workers.dev/mcp'
```

### Other

```json
{
  "mcpServers": {
    "dev-workers-mike-tusa-checkdigit-checkdigit": {
      "type": "http",
      "url": "https://checkdigit.mike-tusa.workers.dev/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-10-23 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-21 (score 71, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-19 (score 70, +1)

- [functional] Server version: 0.2.2 → 0.2.3

### 2026-10-17 (score 69, +1)

- [functional] Server version: 0.2.1 → 0.2.2

### 2026-10-16 (score 68, 0)

- [functional improvement] Stability: unverified → 0.03

### 2026-10-15 (score 68)

First indexed and scored.

## MCP tools (2)

### `validate_code` (~272 tokens)

Validate an IBAN, BIC, EU VAT number, GTIN/EAN/UPC or ISBN

Check the format and check digits of one identifier: IBAN (ISO 13616, per-country length and layout), BIC/SWIFT (ISO 9362 format and country), EU VAT number (offline checksum, VIES not queried), GTIN/EAN-8/UPC-A/EAN-13/GTIN-14 (GS1 mod 10) or ISBN-10/13. type "auto" (default) detects the type from the shape. Returns valid, a reason when invalid (e.g. the expected check digit), and normalized/formatted forms. Format check, not a compliance check: valid does not mean the account, registration or product exists. The code is sent in a POST body and not stored or logged. Read-only. Same engine, keys and limits as POST /v1/{type}.

Input parameters:

- `code` (string, required): The identifier to check, e.g. "DE89 3704 0044 0532 0130 00", "ATU13585627", "4006381333931" or "978-0-306-40615-7". Spaces, hyphens and dots are ignored. Max 64 characters.
- `type` (string): auto (default), iban, bic, vat, gtin or isbn.

Output parameters:

- `bank_code` (string)
- `bban` (string)
- `candidates` (array)
- `check_digit` (string)
- `check_digits` (string)
- `checksum` (string)
- `country` (string)
- `country_name` (string)
- `detected_as` (string)
- `ean13` (string)
- `expected_check_digit` (string)
- `format` (string)
- `formatted` (string)
- `input` (string)
- `isbn10` (string)
- `isbn13` (string)
- `normalized` (string)
- `number` (string)
- `reason` (string)
- `sepa` (boolean)
- `type` (string)
- `valid` (boolean)
- `vies_checked` (boolean)

### `get_meta` (~52 tokens)

Service version, supported formats and limits

Return the service version and build, supported IBAN and VAT countries, GTIN formats, the disclaimer and the current limits. Does not count as a check. Read-only. Same data as GET /v1/meta.

Output parameters:

- `bic` (object)
- `build` (string)
- `disclaimer` (string)
- `endpoints` (array)
- `gtin` (object)
- `iban` (object)
- `limits` (object)
- `privacy` (string)
- `service` (string)
- `vat` (object)
- `version` (string)

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit#diagnostics

## Score history

- 2026-10-24: 72
- 2026-10-23: 72
- 2026-10-22: 71
- 2026-10-21: 71
- 2026-10-20: 70
- 2026-10-19: 70
- 2026-10-18: 69
- 2026-10-17: 69
- 2026-10-16: 68
- 2026-10-15: 68

## Common questions

### What is the CheckDigit MCP server?

CheckDigit is an MCP server listed in the public MCP registry as dev.workers.mike-tusa.checkdigit/checkdigit. Offline check-digit validation for IBAN, BIC, EU VAT, GTIN/EAN/UPC and ISBN. Format check only. This page covers its hosted endpoint (https://checkdigit.mike-tusa.workers.dev/mcp).

### Is the CheckDigit MCP server safe to use?

CheckDigit scores 72 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the CheckDigit MCP server expose?

CheckDigit exposes 2 tools: validate_code, get_meta. Their descriptions and schemas cost roughly 324 tokens of context every time the server is loaded.

### Does the CheckDigit MCP server require authentication?

No. We connected to CheckDigit without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the CheckDigit MCP server still maintained?

CheckDigit is still listed as active in the MCP registry. We last reached this channel on 24 October 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://checkdigit.mike-tusa.workers.dev/mcp
- Website: https://checkdigit.mike-tusa.workers.dev/
- Changelog RSS feed: https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit.xml
- Changelog JSON feed: https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit.json
- HTML version of this page: https://verifymcp.io/servers/dev-workers-mike-tusa-checkdigit-checkdigit/checkdigit