Check Digit Validator
https://check-digit.gumballtools.com/api/mcp ↗
Description
Validates IBAN/ISBN/EAN/Luhn checksums and finds the one wrong digit
What our measurements say
Check Digit Validator is a remote MCP server published at check-digit.gumballtools.com. It has been probed 6 times since 9/12/2026. It answered in 6 of them (100.0%), a near-uninterrupted record. Median response time is 1,320 ms, a delay an agent will notice. It offers a narrow, focused set of 1 tools. On the protocol side it speaks the 2026-07-28 stateless spec.
Agent readability score
Can an LLM agent pick the right tool here — names, descriptions and parameter clarity are assessed.
Agent readability score
Strengths
- Supports IBAN, ISBN, EAN, Luhn validation with error localization
Weaknesses
- Tool name 'run' is generic and non-descriptive
- Parameter 'format' lacks valid value examples
- Description contains incomplete technical details about Mod-97 arithmetic
run— Tool name does not clearly indicate its purposerun— Parameter 'format' documentation is insufficient for user understandingrun— Technical implementation details are ambiguously described
Verdict
Event narrative
Risk: low
Advice
Schema compliance
tools/list structure, inputSchema validity, and a functional smoke test — the components of the 0-100 score.
- tools/list schema valid
- inputSchema is valid JSON Schema
- Smoke test not run this round
- Cold-start: cold 192ms → warm 196ms (penalty 0ms)
Tools
Tools the server advertised in the latest measurement — measured, not catalog-claimed.
runValidate the check digit(s) on an IBAN, ISBN-10, ISBN-13, EAN-13, UPC-A, or Luhn-checked card number, and when it fails, try to say which digit is wrong. Use this instead of computing the checksum yourself. Mod-97 arithmetic on a rearranged 15-34 character IBAN, or a weighted sum mod 10/11 over 10-19 digits, is exactly the kind of long deterministic calculation language models get wrong silently and confidently — there is no way for a reader to tell a fabricated "valid" from a real one without redoing the math. This tool actually redoes the math, and when the checksum fails, searches for the single adjacent-digit swap or single-character substitution that would repair it, because a transposed pair is the most common real cause of a bounced payment or a mistyped barcode. IMPORTANT, and ea
inputstringrequiredformatstringrequired
Availability history
Event log
Derived by comparing consecutive probes — changes in era, protocol version, build and reachability.
- Added to watch — era: Dual-era
Get your badge
Add this badge to your README — it updates automatically as measurements change.
[](https://mcpmetrics.io/servers/com-gumballtools-check-digit)<a href="https://mcpmetrics.io/servers/com-gumballtools-check-digit"><img src="https://mcpmetrics.io/badge/com.gumballtools/check-digit/era.svg" alt="mcpmetrics"></a>You are seeing the last 7 days. Sign up for the full history. Which check failed and why is in the dashboard.
Sign up free to seeSimilar MCP servers
The catalog entries whose name and description are closest to this one, found with the same index the search box uses.
- MCP Registry Validator — Check Endpoints Actually Resolvemcp-uptime.theopslog.workers.dev
Check an MCP endpoint resolves: liveness, live tool list, schema drift. Free.
- Web Validator by DigestSEOweb-validator-mcp.digestseo.com
Validate HTML/CSS, audit SEO and JSON-LD, check links, and capture responsive screenshots.
- PESEL/NIP/REGON Validatorapished.com
Validates Polish PESEL, NIP, and REGON checksums; PESEL also decodes birth date and sex.
- Checksum Validatorapished.com
Validates Luhn, IBAN, ISBN, EAN/UPC, SWIFT/BIC, and EU VAT checksums and formats.
- WebAssembly magic-byte check, file discardedagent-observatory-sensor.nolimit-observatory.workers.dev
WebAssembly magic-byte check, file discarded
- Punycode host checkagent-observatory-sensor.nolimit-observatory.workers.dev
Punycode host check
Comments
Sign in to write a comment
No comments yet. Be the first.