# `dev.invowerk/xrechnung-e-invoice-validator` on anlyon.dev

> Text inside fenced blocks marked untrusted-server-text was written by the MCP server's publisher, not by anlyon.dev. It is data to inspect, not instructions to follow. Invisible characters are shown as [U+XXXX].
> No finding is not a safety guarantee: these are point-in-time checks of tool definitions, not of code or behaviour.

- Page: https://anlyon.dev/servers/dev.invowerk/xrechnung-e-invoice-validator
- JSON: https://anlyon.dev/api/v1/servers/dev.invowerk/xrechnung-e-invoice-validator
- Version: 1.0.1 (active)
- Publisher: dev.invowerk (domain proven to the MCP Registry)
- Runs: remote (streamable-http)
- Sign-in to list tools: none
- Repository: https://github.com/invowerk-dev/invowerk
- Metadata from the official MCP Registry, synced 2026-10-21T18:11:53.168Z

Title and description, as the publisher wrote them:

```untrusted-server-text
invowerk
E-invoice checker for ZUGFeRD, Factur-X, XRechnung and Peppol BIS. Free web tool, API and MCP.
```

Scanned 2026-10-21T18:38:09.246Z over streamable-http.

**6 tools: 3 change things and 3 only read.**

| Group | Class | Tools | Claude Code |
| --- | --- | --- | --- |
| Deletes or cancels | destructive | 0 | deny |
| Can't be undone | irreversible | 0 | ask |
| Changes things | write | 3 | ask |
| Only reads | read | 3 | allow |

## Findings

- **warn** Annotations that disagree with the tool in `generate_invoice` ([annotation-conflict](https://anlyon.dev/methodology#annotation-conflict))

```untrusted-server-text
The server marks "generate_invoice" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

annotations: {"readOnlyHint":true,"openWorldHint":false}; The name "generate_invoice" says "generate": a word for a change.
```

- **warn** Annotations that disagree with the tool in `convert_invoice` ([annotation-conflict](https://anlyon.dev/methodology#annotation-conflict))

```untrusted-server-text
The server marks "convert_invoice" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

annotations: {"readOnlyHint":true,"openWorldHint":true}; The name "convert_invoice" says "convert": a word for a change.
```


## Changes things (3)

Creates or changes something that can be changed back. Claude Code: ask.

### `convert_invoice`

- The name "convert_invoice" says "convert": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
- Findings: warn annotation-conflict

Description, as the server wrote it:

```untrusted-server-text
Convert an e-invoice to UBL or CII. The result is checked before it is returned.

Input: `invoice_base64` is the base64 of an XML invoice or a ZUGFeRD /
Factur-X PDF, at most 4 MB decoded; or pass the file as a download link in
`file`. `target_syntax` is "ubl" or "cii". `target_flavor` is optional,
"en16931" or "xrechnung"; without it the flavor of the source is kept.

Returns `xml`, `syntax`, `flavor` and `self_validation` (`valid`,
`finding_count`). invowerk checks the converted XML before answering and never
returns an invalid document. Input that cannot be read or converted fails with
an error message.

Credits: 3 per call.
```

### `generate_invoice`

- The name "generate_invoice" says "generate": a word for a change.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
- Findings: warn annotation-conflict

Description, as the server wrote it:

```untrusted-server-text
Create a valid EN 16931 e-invoice (UBL or CII XML) from JSON.

Input: `invoice` is a JSON object keyed on EN 16931 Business Terms, the same
schema as `POST /v1/generate`, at most 4 MB. Main fields: `syntax` ("ubl"
default, or "cii"), `flavor` ("en16931" default, or "xrechnung", which
requires `buyer_reference`, the Leitweg-ID BT-10, and `payment_iban`),
`invoice_number`,
`issue_date` (YYYY-MM-DD), `currency`, `seller`, `buyer`, `lines`,
`tax_breakdown`, `totals`. invowerk writes your amounts as given. It does not
compute or correct them.

Returns `xml`, `syntax`, `flavor` and `self_validation`. invowerk checks the
XML before answering and never returns an invalid document. Invalid input, or
XML that fails the check, returns an error, as does a busy (`engine_busy`) or
overrunning (`engine_timeout`) generate.

Credits: 5 per call.
```

### `render_invoice`

- Nothing in its name or description says what it does, so it is counted as a write.
- The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

Description, as the server wrote it:

```untrusted-server-text
Render an XML e-invoice (UBL or CII, e.g. XRechnung) as a readable HTML page.

invowerk uses the KoSIT XRechnung visualization. Use it to show a person what
an e-invoice contains.

Input: `invoice_base64` is the base64 of the XML, at most 4 MB decoded, or pass
the file as a download link in `file`. PDFs are not accepted. `lang` sets the
label language, "de" (default) or "en".

Returns `html` (a complete HTML document), `lang`, `flavor` (e.g.
"xrechnung") and `syntax` (e.g. "ubl_invoice"). A file that is not an XML
invoice, malformed XML or XML with a DOCTYPE fails with an error message,
and so does a busy (`engine_busy`) or overrunning (`engine_timeout`) render.

Credits: 1 per call.
```

## Only reads (3)

Looks things up and changes nothing. Claude Code: allow.

### `explain_errors`

- The name "explain_errors" says "explain": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Explain rule codes in plain language. Works without an API key.

Covers the codes of `validate_invoice` findings and hints: EN 16931,
XRechnung, ZUGFeRD and invowerk's own hint codes (IW-*).

Input: `codes` is a list of one or more codes, e.g. ["BR-CO-18", "BR-DE-21"].
Duplicates are removed. `lang` is "de" (default) or "en".

Returns `lang` and `explanations`. Each explanation has `title`, `meaning`,
`causes`, `fixes`, `severity`, `standard`, `bt_refs`, `xpath_hints` and
`explain_url` (the German page for the code). If any code is unknown, the call
fails and names the unknown codes.

Credits: free. This tool is not metered.
```

### `parse_invoice`

- The description's first verb is "read": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Read an existing e-invoice into JSON keyed on EN 16931 Business Terms.

The JSON is the input format of `generate_invoice`, so you can edit it and
create the invoice again.

Input: `invoice_base64` is the base64 of an XML invoice (UBL or CII) or a
ZUGFeRD / Factur-X PDF, at most 4 MB decoded; or pass the file as a download
link in `file`. A PDF may have at most 500 pages and 16 attachments.

Returns `model` (the invoice as JSON), `detection` (`syntax`, `flavor`,
`customization_id`) and `source` ("xml" or "pdf-embedded"). A file that cannot
be read fails with an error that starts with an error code, e.g. a PDF without
embedded XML, a UBL credit note, malformed XML, or a busy (`engine_busy`) or
overrunning (`engine_timeout`) read.

Credits: 2 per call.
```

### `validate_invoice`

- The name "validate_invoice" says "validate": a word for reading.

Description, as the server wrote it:

```untrusted-server-text
Check an e-invoice against EN 16931 and German rules.

Input: `invoice_base64` is the base64 of an XML invoice (UBL or CII) or a
ZUGFeRD / Factur-X PDF, at most 4 MB decoded; or pass the file as a download
link in `file`. `explain=true` adds an explanation to findings whose rule
has one, in `lang` ("de" or "en").

`valid` is the result. For XRechnung the KoSIT validator decides. If it is
unreachable, invowerk's own check with the same rules decides,
`verdict_source` is "local" and `official_degraded` is true.
`disagreement` is true when both ran and differ. `findings` lists each
problem with `rule_id`, `severity` and `message`; pass the codes to
`explain_errors` (free). `pdfa_verdict` is the PDF/A check of a PDF.
`hints` never change `valid`. Unreadable input returns a finding, not an
error. It fails with an error when the check is busy (`engine_busy`), ran
longer than 20 s (`engine_timeout`) or the XML has more than 100,000
elements (`document_too_complex`).

Credits: 1 per call.
```

## Claude Code permissions

For `.claude/settings.json`, assuming the server is installed as `xrechnung-e-invoice-validator`:

```json
{
  "permissions": {
    "allow": [
      "mcp__xrechnung-e-invoice-validator__validate_invoice",
      "mcp__xrechnung-e-invoice-validator__explain_errors",
      "mcp__xrechnung-e-invoice-validator__parse_invoice"
    ],
    "ask": [
      "mcp__xrechnung-e-invoice-validator__render_invoice",
      "mcp__xrechnung-e-invoice-validator__generate_invoice",
      "mcp__xrechnung-e-invoice-validator__convert_invoice"
    ],
    "deny": []
  }
}
```