# com.yaktool/invoice (npm · yaktool-invoice-mcp)

Check invoice mandatory fields, validate a draft before issuing, and look up EN 16931 code lists.

- Trust score: 72/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-20

## Components

- npm · `yaktool-invoice-mcp`: 72/100 (this document), [markdown](https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp.md), [page](https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp)

## Channel facts

- Registry: `npm`
- Package: `yaktool-invoice-mcp`
- Version: `0.2.0`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, 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 2026-09-20.

- **Supply Chain Security**: 100/100
  - No malware found by supply-chain analysis.
  - No known CVEs affecting this package version or its production dependencies.
  - No install/post-install scripts declared.
  - No production dependencies, so there is no dependency health to assess.
- **Provenance & Transparency**: 19/100
  - Repository check failed: no source repository is declared.
  - Provenance check failed: no build-provenance attestation is published.
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 25 days ago).
  - Security-disclosure policy not yet verified: we couldn't inspect the source repository.
- **Schema Quality & AI Usability**: 60/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1587 tokens (~396/item across 4 items; 4 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 83/100
  - Stability observed for 25 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 77/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 32% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 4 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 4 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

## Install

### How do I install the com.yaktool/invoice MCP server?

com.yaktool/invoice runs locally as an npm package, launched with npx -y yaktool-invoice-mcp. 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 com-yaktool-invoice -- npx -y yaktool-invoice-mcp
```

### Cursor

```json
{
  "mcpServers": {
    "com-yaktool-invoice": {
      "command": "npx",
      "args": [
        "-y",
        "yaktool-invoice-mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "com-yaktool-invoice": {
      "command": "npx",
      "args": [
        "-y",
        "yaktool-invoice-mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add com-yaktool-invoice -- npx -y yaktool-invoice-mcp
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "com-yaktool-invoice": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "yaktool-invoice-mcp"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add com-yaktool-invoice --command npx --arg -y --arg yaktool-invoice-mcp
```

### Hermes

```yaml
mcp_servers:
  com-yaktool-invoice:
    command: "npx"
    args: ["-y", "yaktool-invoice-mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "com-yaktool-invoice": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "yaktool-invoice-mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add com-yaktool-invoice -t stdio -c npx -a -y yaktool-invoice-mcp
```

### Other

```json
{
  "mcpServers": {
    "com-yaktool-invoice": {
      "command": "npx",
      "args": [
        "-y",
        "yaktool-invoice-mcp"
      ]
    }
  }
}
```

## 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.

### 2026-09-18 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 73 to 77. That category is still filling its 30-day observation window: 22 days of observed history at the previous scan, 23 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-16 (score 71, +1)

No change was recorded against any check on this day. Stability & Change Management went from 67 to 70. That category is still filling its 30-day observation window: 20 days of observed history at the previous scan, 21 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-14 (score 70, +1)

No change was recorded against any check on this day. Stability & Change Management went from 60 to 63. That category is still filling its 30-day observation window: 18 days of observed history at the previous scan, 19 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-12 (score 69, +1)

No change was recorded against any check on this day. Stability & Change Management went from 53 to 57. That category is still filling its 30-day observation window: 16 days of observed history at the previous scan, 17 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-10 (score 68, +1)

No change was recorded against any check on this day. Stability & Change Management went from 47 to 50. That category is still filling its 30-day observation window: 14 days of observed history at the previous scan, 15 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-08 (score 67, +1)

No change was recorded against any check on this day. Stability & Change Management went from 40 to 43. That category is still filling its 30-day observation window: 12 days of observed history at the previous scan, 13 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-06 (score 66, +1)

No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-03 (score 65, +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.

## MCP tools (4)

### `check_invoice_fields` (~458 tokens)

Check an invoice for the particulars EU VAT law requires

Check a plain invoice — paper, PDF, or one not yet turned into an e-invoice — against the 16 mandatory particulars the EU VAT Directive lists, plus the arithmetic. This is NOT an XML validator (use check_peppol_invoice or check_xrechnung for that). Input is "Label: value" lines; labels are matched loosely ("Invoice no", "Bill to", "Subtotal", "Amount excluding VAT" all resolve). Anything it cannot find is reported as missing rather than guessed. THE SCENARIO DECIDES WHICH PARTICULARS APPLY: from the two VAT number prefixes the tool works out domestic vs intra-EU B2B vs export, and only then requires the customer VAT number. When both prefixes are not present it returns scenario "unknown" and requires nothing extra — guessing would either invent a requirement or hide one. ARITHMETIC FINDINGS CARRY OFFICIAL EN 16931 RULE NUMBERS (BR-CO-15 for total = net + VAT, BR-CO-17 for VAT = taxable × rate), quoted verbatim from the published Peppol rule set — the same identifiers an access point will cite when it rejects the e-invoice version later. Report those identifiers as-is; they are checkable against official documentation. Also flags: zero VAT with no exemption basis stated, VAT charged to a VAT-registered customer in another member state, malformed VAT numbers (INV-015) and VAT numbers that fail their country check digit (INV-016 — a stronger signal). Limits stated rather than hidden: national add-ons beyond the directive are NOT covered, VAT numbers are not verified against VIES (that needs a network call), and this is not tax advice. Returns { fields, particulars[{id, label, status: present|missing|not-applicable, detail?}], findings[], summary{scenario, present, required, errors, warnings, supplierCountry?, customerCountry?, arithmetic{net,vat,gross,expectedVat,expectedGross}, byRule} }.

Input parameters:

- `text` (string, required): The invoice fields as "Label: value" lines, e.g. "Invoice number: 2026-0042 Net: 1000.00 VAT rate: 19".

### `check_invoice_draft` (~563 tokens)

Check a structured invoice draft before it is issued

Check an invoice you are ABOUT TO ISSUE, passed as structured fields, against 25 documented rules. The complement of check_invoice_fields: that one parses an existing invoice from text, this one takes the draft your agent is building — and because the amounts are computed here (per VAT rate, as Article 226 requires), the arithmetic rules cannot fail by construction. THREE DOCUMENT TYPES: "vat" applies the EU VAT Directive Article 226 particulars (INV-001…016); "commercial" and "proforma" apply customs practice instead (CINV-002…010: HS code and origin per line, Incoterms, net weight, EORI when goods cross the EU border) — a proforma result also reminds you it must be visibly marked, since it is not a VAT invoice. THE SCENARIO IS INFERRED, NOT ASKED: from each party's country (explicit field, or the VAT prefix with EL→GR handled) the tool derives domestic/intra-EU/export and B2B/B2C, and only then decides which particulars are required — e.g. the customer VAT number only on an intra-EU B2B supply, an exemption wording whenever any line is zero-rated. FORWARDED CHECKS KEEP THEIR HOME RULE IDS: VAT numbers (INV-015/016 with 28-country check digits), EORI (EORI-*), IBAN (IBAN-*), RF creditor references (RF-*), HS codes (HS-*, per line), Incoterms 2020 (INC-*). Line-level problems come back in lineIssues[] with a 0-based line index so you can point at the exact line. Not covered, stated rather than hidden: VAT rate correctness per country (no rate tables — you supply the rate, it does the arithmetic), currency conversion, national add-ons beyond the directive, and this is not tax advice. Returns { scenario, computed{lines[{lineNet}], rateGroups[{rate,taxable,vat}], totals{net,vat,gross,weightKg?}}, findings[], lineIssues[{line, findings[]}], particulars[{id,label,status,detail?}], readyToIssue }.

Input parameters:

- `buyer` (required)
- `currency` (string, required)
- `docType` (string, required)
- `dueDate` (string)
- `exemptionReason` (string)
- `incoterm` (string)
- `incotermPlace` (string)
- `invoiceNumber` (string, required)
- `issueDate` (string, required)
- `lines` (array, required): Invoice lines, at most 200
- `notes` (string)
- `payment` (object)
- `seller` (object, required)
- `supplyDate` (string)

### `lookup_en16931_code` (~391 tokens)

Look up an EN 16931 / Peppol code, and the rules it triggers

Search or resolve the code lists an electronic invoice is judged by: invoice type (UNCL1001), VAT category (UNCL5305), payment means (UNCL4461) and allowance reason (UNCL5189). THE POINT IS NOT THE LABEL. Telling someone "AE means reverse charge" is nearly useless; what matters is that choosing AE brings a whole family of official rules into force. For a VAT category code this tool returns those rules VERBATIM with their official identifiers (BR-AE-01 … BR-AE-10), so an agent can check the invoice against them or quote them to a user. Values that get chosen wrongly, worth knowing: 380 (commercial invoice) sent for what is actually a credit note; 30 (generic credit transfer) where the receiver expects 58 (SEPA credit transfer); and E / O / Z used as synonyms when exempt, outside-scope and zero-rated are three different rule families. L and M exist because the Canary Islands (IGIC) and Ceuta/Melilla (IPSI) sit outside the EU VAT area. When a code is not in a list, that is reported as such along with the nearest codes — a value outside the list is rejected by the receiving system rather than interpreted. Pass `code` with `list` to resolve one value, or `query` to search all four lists by code or meaning. Returns either { list, entry?, neighbours[], rules?[] } or { hits[{code, name, listId, listTitle}] }.

Input parameters:

- `code` (string): A specific code to resolve; needs `list` as well.
- `list` (string): Which list `code` belongs to: invoice type, VAT category, payment means, allowance reason.
- `query` (string): Free-text search across all four lists, by code or by meaning.

### `list_en16931_vat_category_rules` (~175 tokens)

List the official rules a VAT category code brings into force

Given a VAT category code (S, Z, E, AE, K, G, O, L, M, B), return every EN 16931 / Peppol rule that applies to invoices using it — official identifiers and rule text quoted verbatim from the published rule set. Use this before building or judging an invoice with a non-standard VAT category: the reverse-charge family alone carries ten rules about what the VAT breakdown must contain, what the rate must be, and when an exemption reason is mandatory. Returns { code, family, rules[{id, text, severity}] }. An unknown code returns an empty rule list rather than a guess.

Input parameters:

- `code` (string, required): The VAT category code, e.g. "AE" for reverse charge or "K" for an intra-community supply.

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp#diagnostics

## Score history

- 2026-09-20: 72
- 2026-09-19: 72
- 2026-09-18: 72
- 2026-09-17: 71
- 2026-09-16: 71
- 2026-09-15: 70
- 2026-09-14: 70
- 2026-09-13: 69
- 2026-09-12: 69
- 2026-09-11: 68
- 2026-09-10: 68
- 2026-09-09: 67
- 2026-09-08: 67
- 2026-09-07: 66
- 2026-09-06: 66
- 2026-09-05: 65
- 2026-09-04: 65
- 2026-09-03: 65
- 2026-09-02: 64
- 2026-09-01: 61
- 2026-08-31: 61
- 2026-08-30: 61
- 2026-08-29: 61
- 2026-08-28: 61
- 2026-08-27: 61
- 2026-08-26: 39

## Common questions

### What is the com.yaktool/invoice MCP server?

com.yaktool/invoice is an MCP server listed in the public MCP registry as com.yaktool/invoice. Check invoice mandatory fields, validate a draft before issuing, and look up EN 16931 code lists. This page covers its npm package (yaktool-invoice-mcp).

### Is the com.yaktool/invoice MCP server safe to use?

com.yaktool/invoice scores 72 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 20 September 2026. It declares no install or post-install scripts. 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 com.yaktool/invoice MCP server expose?

com.yaktool/invoice exposes 4 tools: check_invoice_fields, check_invoice_draft, lookup_en16931_code, list_en16931_vat_category_rules. Their descriptions and schemas cost roughly 1,587 tokens of context every time the server is loaded.

### Is the com.yaktool/invoice MCP server still maintained?

com.yaktool/invoice is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What licence is the com.yaktool/invoice MCP server under?

com.yaktool/invoice declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

## Links

- npm package: https://www.npmjs.com/package/yaktool-invoice-mcp
- Socket report: https://socket.dev/npm/package/yaktool-invoice-mcp
- Changelog RSS feed: https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp.json
- HTML version of this page: https://verifymcp.io/servers/com-yaktool-invoice/yaktool-invoice-mcp