Factur-X: Generate & Validate E-Invoices

Try fixed invoice samples (no document input)

view_invoice_demo

Read-onlyIdempotent

Demonstrate the engine on bundled synthetic samples only; never checks a user's invoice.

Use for product evaluation without a key. To check a supplied document, choose validate_invoice.
Choose sample=valid to inspect a passing CII invoice or sample=invalid to see the missing-buyer-name
finding. Both use the production XSD and EN 16931 engine; results may be cached for 24 hours for
the same engine version and input. Inspect validated_at and cached; a cache hit is not a fresh run.
Call with {} to validate the passing sample, or sample=downloads for PDF/CII/UBL files and the published report.
Accepts no document data, URLs or extra arguments. No PDF or business-register checks in live mode.
Shared rate limits return a retryable tool error; unavailable checks never become a passing result.
Use explain_finding for a returned rule id. Your own invoices require validate_invoice with
a verified-account trial, prepaid or monthly-plan key. Nothing is stored except reports for these public fixtures.

Input Schema

Name	Required	Description	Default
`sample`	No	valid (default): passing CII invoice; invalid: missing buyer name; downloads: published files.	valid

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 2, 2026

removedInput schema / properties / sample / anyOf

Removed value: -[
-  {
-    "enum": [
-      "valid",
-      "invalid"
-    ],
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

changedInput schema / properties / sample / default
```
Previous value: -nullNew value: +"valid"
```

changedInput schema / properties / sample / description

Previous value: -"valid: fixed CII invoice; invalid: same invoice without the buyer name. Omit for downloads."New value: +"valid (default): passing CII invoice; invalid: missing buyer name; downloads: published files."

addedInput schema / properties / sample / enum

Added value: +[
+  "valid",
+  "invalid",
+  "downloads"
+]

addedInput schema / properties / sample / type
```
Added value: +"string"
```

Changed1 schema field changedSep 30, 2026

addedInput schema / properties / sample

Added value: +{
+  "anyOf": [
+    {
+      "enum": [
+        "valid",
+        "invalid"
+      ],
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "valid: fixed CII invoice; invalid: same invoice without the buyer name. Omit for downloads.",
+  "title": "Sample"
+}

AddedSep 27, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Annotations already declare readOnly/idempotent/closed-world, and the description adds substantial non-obvious behavior beyond them: 24-hour caching keyed on engine version and input, the meaning of validated_at/cached ('a cache hit is not a fresh run'), retryable rate-limit errors, and that unavailable checks never become a passing result. It also states what is not stored.

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-loaded with purpose and routing, then constraints and caching. Efficient overall, though slightly dense and mildly redundant in the negative-constraint sentences ('Accepts no document data, URLs or extra arguments' and 'No PDF or business-register checks in live mode' overlap in intent).

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?

An output schema exists so return values need no explanation, and the description still tells the agent which output fields to inspect and how to interpret a cache hit. Combined with sibling routing, key requirements, and negative constraints, nothing essential for correct invocation is missing.

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

Parameters4/5

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

Schema coverage is 100% and the enum is documented there, so the baseline is 3, but the description adds outcome-level meaning the schema lacks: what each sample actually yields (passing CII invoice, missing-buyer-name finding, PDF/CII/UBL files plus published report) and that {} defaults to the passing sample.

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

Purpose5/5

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

States a precise verb and resource: 'Demonstrate the engine on bundled synthetic samples only; never checks a user's invoice.' It explicitly contrasts with validate_invoice and validate_invoice is named as the sibling for real documents, so an agent can pick correctly without opening the schema.

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

Usage Guidelines5/5

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

Gives explicit when-to-use (product evaluation without a key), the alternative and the exact routing condition ('To check a supplied document, choose validate_invoice'), plus per-sample guidance: sample=valid for a passing CII invoice, sample=invalid for the missing-buyer-name finding, sample=downloads for published files.

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

All Factur-X: Generate & Validate E-Invoices tools Inspect

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