# invowerk (remote · api.invowerk.dev)

E-invoice checker for ZUGFeRD, Factur-X, XRechnung and Peppol BIS. Free web tool, API and MCP.

- Trust score: 82/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-10-23

## Components

- remote · `api.invowerk.dev`: 82/100 (this document), [markdown](https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api.md), [page](https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api)

## Channel facts

- Endpoint: `https://api.invowerk.dev/mcp/`
- Transports: `streamable-http`
- Auth: `none`
- Version: `1.0.1`

## 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 2026-10-23.

- **Endpoint Security**: 80/100
  - 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 is enforced; there's no plaintext access path.
  - 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**: 65/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1816 tokens (~302/item across 6 items; 6 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 73/100
  - Stability observed for 22 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 6 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 6 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 invowerk MCP server?

invowerk is a hosted endpoint at https://api.invowerk.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-invowerk-xrechnung-e-invoice-validator 'https://api.invowerk.dev/mcp/'
```

### Cursor

```json
{
  "mcpServers": {
    "dev-invowerk-xrechnung-e-invoice-validator": {
      "url": "https://api.invowerk.dev/mcp/"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "dev-invowerk-xrechnung-e-invoice-validator": {
      "type": "http",
      "url": "https://api.invowerk.dev/mcp/"
    }
  }
}
```

### Codex

```toml
[mcp_servers.dev-invowerk-xrechnung-e-invoice-validator]
url = "https://api.invowerk.dev/mcp/"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "dev-invowerk-xrechnung-e-invoice-validator": {
      "type": "remote",
      "url": "https://api.invowerk.dev/mcp/",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add dev-invowerk-xrechnung-e-invoice-validator --url 'https://api.invowerk.dev/mcp/' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  dev-invowerk-xrechnung-e-invoice-validator:
    url: "https://api.invowerk.dev/mcp/"
```

### Netclaw

```json
{
  "McpServers": {
    "dev-invowerk-xrechnung-e-invoice-validator": {
      "Transport": "http",
      "Url": "https://api.invowerk.dev/mcp/"
    }
  }
}
```

### Vellum

```bash
assistant mcp add dev-invowerk-xrechnung-e-invoice-validator -t streamable-http -u 'https://api.invowerk.dev/mcp/'
```

### Other

```json
{
  "mcpServers": {
    "dev-invowerk-xrechnung-e-invoice-validator": {
      "type": "http",
      "url": "https://api.invowerk.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.

### 2026-10-22 (score 82, +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.

### 2026-10-20 (score 81, +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.

### 2026-10-18 (score 80, +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.

### 2026-10-16 (score 79, +1)

- [security] Tool “generate_invoice” rewrote its description, which is the text the model reads

### 2026-10-14 (score 78, +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.

### 2026-10-12 (score 77, +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.

### 2026-10-10 (score 76, +1)

No change was recorded against any check on this day. Stability & Change Management went from 20 to 30. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-07 (score 75, +1)

No change was recorded against any check on this day. Stability & Change Management went from 13 to 20. That category is still filling its 30-day observation window: 4 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.

## MCP tools (6)

### `validate_invoice` (~399 tokens)

Check an e-invoice

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.

Input parameters:

- `explain` (boolean): true adds an explanation to each finding whose rule has one.
- `file` (object): The file as a download link, instead of `invoice_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL.
- `invoice_base64`: The invoice file, base64-encoded. At most 4 MB decoded.
- `lang` (string): Language of the explanations: "de" (default) or "en".

### `render_invoice` (~292 tokens)

Render an e-invoice as HTML

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.

Input parameters:

- `file` (object): The file as a download link, instead of `invoice_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL.
- `invoice_base64`: The invoice file, base64-encoded. At most 4 MB decoded.
- `lang` (string): Language of the labels: "de" (default) or "en".

### `explain_errors` (~245 tokens)

Explain error codes

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.

Input parameters:

- `codes` (array, required): One or more rule codes from validate_invoice, e.g. ["BR-CO-18", "BR-DE-21"].
- `lang` (string): Language of the explanations: "de" (default) or "en".

### `generate_invoice` (~304 tokens)

Create an e-invoice from JSON

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.

Input parameters:

- `invoice` (object, required): The invoice as a JSON object keyed on EN 16931 Business Terms, the schema of POST /v1/generate and of parse_invoice's `model`: syntax, flavor, invoice_number, issue_date, currency, seller, buyer, lin…

### `parse_invoice` (~283 tokens)

Read an e-invoice into JSON

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.

Input parameters:

- `file` (object): The file as a download link, instead of `invoice_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL.
- `invoice_base64`: The invoice file, base64-encoded. At most 4 MB decoded.

### `convert_invoice` (~293 tokens)

Convert an e-invoice between UBL and CII

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.

Input parameters:

- `file` (object): The file as a download link, instead of `invoice_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL.
- `invoice_base64`: The invoice file, base64-encoded. At most 4 MB decoded.
- `target_flavor`: Optional: "en16931" or "xrechnung". Without it the flavor of the source is kept.
- `target_syntax` (string, required): Syntax to convert to: "ubl" or "cii".

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api#diagnostics

## Score history

- 2026-10-23: 82
- 2026-10-22: 82
- 2026-10-21: 81
- 2026-10-20: 81
- 2026-10-19: 80
- 2026-10-18: 80
- 2026-10-17: 79
- 2026-10-16: 79
- 2026-10-15: 78
- 2026-10-14: 78
- 2026-10-13: 77
- 2026-10-12: 77
- 2026-10-11: 76
- 2026-10-10: 76
- 2026-10-07: 75
- 2026-10-05: 74
- 2026-10-04: 73
- 2026-10-03: 73
- 2026-10-02: 72
- 2026-10-01: 72

## Common questions

### What is the invowerk MCP server?

invowerk is an MCP server listed in the public MCP registry as dev.invowerk/xrechnung-e-invoice-validator. E-invoice checker for ZUGFeRD, Factur-X, XRechnung and Peppol BIS. Free web tool, API and MCP. This page covers its hosted endpoint (https://api.invowerk.dev/mcp/).

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

invowerk scores 82 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 invowerk MCP server expose?

invowerk exposes 6 tools: validate_invoice, render_invoice, explain_errors, generate_invoice, parse_invoice, convert_invoice. Their descriptions and schemas cost roughly 1,816 tokens of context every time the server is loaded.

### Does the invowerk MCP server require authentication?

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

### Is the invowerk MCP server still maintained?

invowerk is still listed as active in the MCP registry. We last reached this channel on 23 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://api.invowerk.dev/mcp/
- Repository: https://github.com/invowerk-dev/invowerk
- Website: https://invowerk.dev/en/
- Changelog RSS feed: https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api.xml
- Changelog JSON feed: https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api.json
- HTML version of this page: https://verifymcp.io/servers/dev-invowerk-xrechnung-e-invoice-validator/api