invowerk
E-invoice checker for ZUGFeRD, Factur-X, XRechnung and Peppol BIS. Free web tool, API and MCP.
Should I use this
Quality & Safety
Based on automated analysis of tool definitions and protocol compliance.
Context Cost
This is the approximate number of tokens consumed each time the server's tools are loaded into a model's context. Higher counts reduce the attention available for other tasks.
Install
One-Click Install
Add this to your `claude_desktop_config.json` file:
{
"mcpServers": {
"invowerk": {
"url": "https://api.invowerk.dev/mcp/"
}
}
}Remote endpoints
https://api.invowerk.dev/mcp/streamable-httpWhat it can do
Tool inventory
Tools (6)
🟢validate_invoice(invoice_base64, file, explain, lang)
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. Credits: 1 per call.
Input Schema
{
"type": "object",
"properties": {
"invoice_base64": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "The invoice file, base64-encoded. At most 4 MB decoded."
},
"file": {
"properties": {
"download_url": {
"description": "A public https URL of the file.",
"type": "string"
},
"file_id": {
"description": "An identifier for the file. ChatGPT sets it; other clients may pass any label, such as the file name.",
"type": "string"
},
"mime_type": {
"type": "string"
},
"file_name": {
"type": "string"
}
},
"required": [
"download_url",
"file_id"
],
"type": "object",
"default": null,
"description": "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."
},
"explain": {
"default": false,
"description": "true adds an explanation to each finding whose rule has one.",
"type": "boolean"
},
"lang": {
"default": "de",
"description": "Language of the explanations: \"de\" (default) or \"en\".",
"type": "string"
}
},
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}🟢render_invoice(invoice_base64, file, lang)
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. Credits: 1 per call.
Input Schema
{
"type": "object",
"properties": {
"invoice_base64": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "The invoice file, base64-encoded. At most 4 MB decoded."
},
"file": {
"properties": {
"download_url": {
"description": "A public https URL of the file.",
"type": "string"
},
"file_id": {
"description": "An identifier for the file. ChatGPT sets it; other clients may pass any label, such as the file name.",
"type": "string"
},
"mime_type": {
"type": "string"
},
"file_name": {
"type": "string"
}
},
"required": [
"download_url",
"file_id"
],
"type": "object",
"default": null,
"description": "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."
},
"lang": {
"default": "de",
"description": "Language of the labels: \"de\" (default) or \"en\".",
"type": "string"
}
},
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}🟢explain_errors(codes, lang)
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 Schema
{
"type": "object",
"properties": {
"codes": {
"description": "One or more rule codes from validate_invoice, e.g. [\"BR-CO-18\", \"BR-DE-21\"].",
"items": {
"type": "string"
},
"type": "array"
},
"lang": {
"default": "de",
"description": "Language of the explanations: \"de\" (default) or \"en\".",
"type": "string"
}
},
"required": [
"codes"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}🟢generate_invoice(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), `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. Credits: 5 per call.
Input Schema
{
"type": "object",
"properties": {
"invoice": {
"additionalProperties": true,
"description": "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, lines, tax_breakdown, totals.",
"type": "object"
}
},
"required": [
"invoice"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}🟢parse_invoice(invoice_base64, file)
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 or malformed XML. Credits: 2 per call.
Input Schema
{
"type": "object",
"properties": {
"invoice_base64": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "The invoice file, base64-encoded. At most 4 MB decoded."
},
"file": {
"properties": {
"download_url": {
"description": "A public https URL of the file.",
"type": "string"
},
"file_id": {
"description": "An identifier for the file. ChatGPT sets it; other clients may pass any label, such as the file name.",
"type": "string"
},
"mime_type": {
"type": "string"
},
"file_name": {
"type": "string"
}
},
"required": [
"download_url",
"file_id"
],
"type": "object",
"default": null,
"description": "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."
}
},
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}🟢convert_invoice(target_syntax, invoice_base64, file, target_flavor)
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 Schema
{
"type": "object",
"properties": {
"target_syntax": {
"description": "Syntax to convert to: \"ubl\" or \"cii\".",
"type": "string"
},
"invoice_base64": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "The invoice file, base64-encoded. At most 4 MB decoded."
},
"file": {
"properties": {
"download_url": {
"description": "A public https URL of the file.",
"type": "string"
},
"file_id": {
"description": "An identifier for the file. ChatGPT sets it; other clients may pass any label, such as the file name.",
"type": "string"
},
"mime_type": {
"type": "string"
},
"file_name": {
"type": "string"
}
},
"required": [
"download_url",
"file_id"
],
"type": "object",
"default": null,
"description": "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."
},
"target_flavor": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "Optional: \"en16931\" or \"xrechnung\". Without it the flavor of the source is kept."
}
},
"required": [
"target_syntax"
],
"additionalProperties": false
}Output Schema
{
"type": "object",
"additionalProperties": true
}Community
Evidence