invowerk

Render an e-invoice as HTML

render_invoice

Read-only

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

TableJSON Schema

Name	Required	Description	Default
`file`	No	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`	No	Language of the labels: "de" (default) or "en".	de
`invoice_base64`	No	The invoice file, base64-encoded. At most 4 MB decoded.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedSep 28, 2026

addedInput schema / properties / file

Added value: +{
+  "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.",
+  "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"
+    },
+    "file_name": {
+      "type": "string"
+    },
+    "mime_type": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "download_url",
+    "file_id"
+  ],
+  "type": "object"
+}

addedInput schema / properties / invoice_base64 / anyOf

Added value: +[
+  {
+    "type": "string"
+  },
+  {
+    "type": "null"
+  }
+]

addedInput schema / properties / invoice_base64 / default
```
Added value: +null
```

addedInput schema / properties / invoice_base64 / description

Added value: +"The invoice file, base64-encoded. At most 4 MB decoded."

removedInput schema / properties / invoice_base64 / type
```
Removed value: -"string"
```

addedInput schema / properties / lang / description

Added value: +"Language of the labels: \"de\" (default) or \"en\"."

removedInput schema / required

Removed value: -[
-  "invoice_base64"
-]

First observedSep 28, 2026

TDQS

A4/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint/openWorldHint annotations it discloses real behavioral detail: the 4 MB decoded size cap, that PDFs are rejected, that non-invoice/malformed/DOCTYPE XML fails with an error, and the exact cost of 1 credit per call. This is unusually rich disclosure for a read tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads purpose, then groups input, output, error and cost information with clear inline labels. It is slightly longer than strictly necessary given the output schema already enumerates returns, but every sentence carries usable content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite the multi-input, nested-object complexity, the description covers source alternatives (base64 vs file link), limits, language, failure modes, and cost. With an output schema present, the return-field recap is redundant but harmless; nothing an agent needs to call correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3; the description largely restates what the schema already documents (base64, 4 MB limit, lang de/en default). The only genuine addition is the explicit prohibition on PDFs, which is not captured in the schema, so it neither compensates nor falls short.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource+output: render an XML e-invoice (UBL/CII) as a readable HTML page, and names the underlying mechanism (KoSIT XRechnung visualization). It distinguishes itself from siblings by producing human-readable HTML rather than parsing/validating/converting, though it never names an alternative tool explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Use it to show a person what an e-invoice contains" gives a clear intended context, implying this is for human display rather than machine processing. However, it offers no explicit when-not guidance and does not contrast with the closest sibling, convert_invoice.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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