# invowerk

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

- name: dev.invowerk/xrechnung-e-invoice-validator
- version: 1.0.1
- connection class: R0 (autonomous)
- trust: 96/100
- quality: 80/100 (good)
- owner: not claimed
- descriptor: https://api.protogrid.dev/v1/servers/dev.invowerk%2Fxrechnung-e-invoice-validator
- tools: https://api.protogrid.dev/v1/servers/dev.invowerk%2Fxrechnung-e-invoice-validator/tools

**An agent can connect right now, no human step.** Remote endpoint, no authentication, reachable on the last probe.

## Connection (mcpServers)

```json
{
  "mcpServers": {
    "xrechnung-e-invoice-validator": {
      "type": "http",
      "url": "https://api.invowerk.dev/mcp/",
      "headers": {
        "X-API-Key": "${X_API_KEY}"
      }
    }
  }
}
```

Placeholders to fill: `${X_API_KEY}`.

## Trust

- hygiene: 100
- liveness: 100
- freshness: 100
- provenance: 85
- drivers: +repository +dns-namespace +website +reachable +uptime-100% +updated-16d-ago
- Derived from observable signals (official registry feed and our own credential-free probes); no code audit performed.

## Quality 80/100 (good)

### protocol: 75 (weight 25)

- warn `protocol.modern`: newest supported version is 2025-11-25; 2026-07-28 not supported, older versions are deprecated until 2027-07-28
- n/a `protocol.stateless`: only applies to 2026-07-28 servers
- pass `protocol.transport`: streamable HTTP
- n/a `protocol.list_ttl`: only applies to 2026-07-28 servers

### authorization: n/a (weight 15)

- n/a `auth.prm`, `auth.as_metadata`, `auth.cimd`: no remote uses OAuth
- n/a `auth.secret_in_url`: no templated URL

### tool hygiene: 86 (weight 30)

- pass `tools.descriptions`: every tool has a description
- pass `tools.description_length`: descriptions are concise
- pass `tools.schemas`: every tool has an object input schema
- pass `tools.annotations`: 6 of 6 tools declare readOnlyHint or destructiveHint
- fail `tools.directory_hints`: no tool declares all four of readOnlyHint, destructiveHint, idempotentHint and openWorldHint; missing: render_invoice (destructiveHint, idempotentHint); generate_invoice (destructiveHint, idempotentHint); validate_invoice (destructiveHint, idempotentHint); …
- pass `tools.token_cost`: about 2,410 tokens to load every tool
- pass `tools.api_dump`: tools are not a one-to-one API dump

### stability: 75 (weight 15)

- warn `stability.changes`: 10 tool changes in 30 days
- pass `stability.rug_pull`: no tool changed its meaning under the same name

### dependencies: n/a (weight 15)

- n/a `deps.known_vulns`, `deps.mcp_sdk_version`, `deps.resolvable`: no npm or PyPI package

- tools: 6, about 2,410 tokens to load them all
- tool set hash: d1b5698ef099a62a174108a403b9e4f1
- tools last changed: 2026-10-15T16:14:58.426Z
- badge: [![protogrid quality](https://protogrid.dev/badge/dev.invowerk/xrechnung-e-invoice-validator.svg)](https://protogrid.dev/servers/dev.invowerk/xrechnung-e-invoice-validator)
- Checks run on what our credential-free, read-only probes observe; tools are never called and no code audit is performed.

### Tool changes

- 2026-10-15 `generate_invoice` changed (description)
  - before: 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), `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.
  - after: 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.
- 2026-10-04 `explain_errors` changed (inputSchema)
- 2026-10-04 `render_invoice` changed (inputSchema)
- 2026-10-04 `validate_invoice` changed (inputSchema)
- 2026-10-02 `convert_invoice` changed (annotations)
- 2026-10-02 `parse_invoice` changed (annotations)
- 2026-10-02 `generate_invoice` changed (annotations)
- 2026-10-02 `explain_errors` changed (annotations)
- 2026-10-02 `render_invoice` changed (annotations)
- 2026-10-02 `validate_invoice` changed (annotations)

Full history: https://api.protogrid.dev/v1/servers/dev.invowerk%2Fxrechnung-e-invoice-validator/changes

## Remotes

- https://api.invowerk.dev/mcp/ (streamable-http, auth none, reachable true, uptime30d 1)

## Packages

_none_

## Tools (6)

- `convert_invoice`: 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.
- `explain_errors`: 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.
- `generate_invoice`: 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.
- `parse_invoice`: 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.
- `render_invoice`: 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.
- `validate_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.