Is the Check Digits MCP server free to use?

Yes. Check Digits is listed on AllMCPs as a free, open Model Context Protocol server you can install into Claude Desktop, Cursor, or any MCP-compatible client.

Is the Check Digits MCP server free to use?

Yes. Check Digits is listed on AllMCPs as a free, open Model Context Protocol server you can install into Claude Desktop, Cursor, or any MCP-compatible client.

Check Digits

Catch a mistyped IBAN, card, barcode, VIN or routing number before it causes a failed payment.

Quick Install

Automated & IDE Setup

Copy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.

Add to Cursor Add to VS Code

Manual Client & Custom JSON ConfigExpand JSON ▾

Install Config Generator

Choose your client

claude_desktop_config.json

{
  "mcpServers": {
    "check-digits": {
      "command": "npx",
      "args": [
        "-y",
        "check-digits"
      ]
    }
  }
}

💡 Paste into ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows)

Documentation Overview

toolstop

Small, stateless MCP servers. Each one does a single narrow job exactly, so an assistant can call it instead of guessing.

Every server runs on Cloudflare Workers at <name>.toolstop.dev, holds no state, and can also run locally over stdio.

Servers

Server	Does	Endpoint
check-digits	Validates check digits for IBAN, LEI, ISBN, GTIN/UPC/EAN, VIN, NPI, ISIN, ABA routing numbers and payment cards	`https://check-digits.toolstop.dev`

Connecting

Remote, over streamable HTTP. No install, no account:

config.json

{
  "mcpServers": {
    "check-digits": {
      "type": "url",
      "url": "https://check-digits.toolstop.dev"
    }
  }
}

Local, over stdio:

Terminal

npx @toolstop/check-digits

Design

Stateless. No database, no vector index, no metered upstream API. A request is answered from its arguments alone. Servers scale to zero and an idle one costs nothing.

Zero runtime dependencies. No MCP SDK, no schema library. MCP over streamable HTTP is request/response, which makes hand-rolled dispatch small enough to be worth it: faster cold starts, and no supply chain.

Telemetry records shape and outcome, never argument values. A check-digit server that logged its input would be storing real IBANs and card numbers. The transport emits one row per request describing what kind of call happened and whether it succeeded. packages/_shared/transport.test.mjs asserts that no raw argument value can reach it.

The row also carries a session id, and it is derived from the network the request came from, truncated to a /24 or /48 before hashing, never the full address. Hashing the whole IP would not have anonymised it: the IPv4 space is 32 bits and the other inputs are public, so the id was walkable back to one address until this was fixed on 2026-08-10. Each server's README states the complete recorded row rather than only what is left out.

Every tool declares readOnlyHint, a complete inputSchema and an outputSchema, so a client can tell what a call will do before making it and what shape comes back. The transport refuses to start a server whose tools do not state their annotations, rather than defaulting them to something reassuring.

Repo layout

Code

packages/_shared/     shared transport, dispatch and telemetry
packages/mcp-<name>/  one server
scripts/discover.mjs  derives the CI matrix from the filesystem
scripts/smoke.mjs     protocol check against a live endpoint

See CLAUDE.md for the operating manual.

Development

Terminal

npm install
npm test                                # every server plus the shared transport
node scripts/smoke.mjs mcp-check-digits # protocol check against the live endpoint

License

MIT

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Frequently Asked Questions about Check Digits

Add the following block to your claude_desktop_config.json under mcpServers: "mcpServers": { "check-digits": { "command": "npx", "args": ["-y", "Check Digits"] } }

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Technical Specs & Signals

CategoryFinance & Fintech

27Quality signal: Emerging · 27/100How this signal is calculated ▾

Server availabilityNot measured

Not scored for repo-hosted servers — we can't reach the running server, only its GitHub page. Hosted MCP endpoints are health-checked live.

Verified ownership8/20

Documentation & tools11/30

Adoption & activity1/15

Community engagement0/10

A guidance signal from public completeness & health data — not a user rating. New listings start lower and rise as they add docs, get verified, and grow adoption. Signals we can't observe for a listing are skipped, not counted against it.

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More in 💰 Finance & Fintech →Best MCP servers for Finance & Fintech →Alternatives to Check Digits →Install in Claude Desktop Install in Cursor Install in VS Code

Documentation Overview

toolstop

Small, stateless MCP servers. Each one does a single narrow job exactly, so an assistant can call it instead of guessing.

Every server runs on Cloudflare Workers at <name>.toolstop.dev, holds no state, and can also run locally over stdio.

Servers

Server	Does	Endpoint
check-digits	Validates check digits for IBAN, LEI, ISBN, GTIN/UPC/EAN, VIN, NPI, ISIN, ABA routing numbers and payment cards	`https://check-digits.toolstop.dev`

Connecting

Remote, over streamable HTTP. No install, no account:

config.json

{
  "mcpServers": {
    "check-digits": {
      "type": "url",
      "url": "https://check-digits.toolstop.dev"
    }
  }
}

Local, over stdio:

Terminal

npx @toolstop/check-digits

Design

Stateless. No database, no vector index, no metered upstream API. A request is answered from its arguments alone. Servers scale to zero and an idle one costs nothing.

Repo layout

Code

packages/_shared/     shared transport, dispatch and telemetry
packages/mcp-<name>/  one server
scripts/discover.mjs  derives the CI matrix from the filesystem
scripts/smoke.mjs     protocol check against a live endpoint

See CLAUDE.md for the operating manual.

Development

Terminal

npm install
npm test                                # every server plus the shared transport
node scripts/smoke.mjs mcp-check-digits # protocol check against the live endpoint

License

MIT