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

The readOnlyHint annotation already signals a read-only operation, and the description adds meaningful behavioral detail: it reports per required field whether it is present and takes Kleinbetragsrechnung, Kleinunternehmer, and Reverse Charge special cases into account. No contradiction with the annotations.

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

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

One dense sentence front-loads the core purpose and includes only operationally relevant details: input source flexibility, output granularity, and legal exceptions. There is no filler or repetition.

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

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

For a tool with 11 parameters, nested objects, and no output schema, the description covers purpose, admissible input sources, result granularity, and key legal carve-outs. It does not specify the exact result container format or how to map raw Word/PDF content onto the structured parameters, but the schema and title provide enough for correct invocation.

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

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

Schema description coverage is 73%, so the schema carries most of the parameter meaning. The description explains the legal purpose but does not elaborate on undocumented fields like iban, rechnungsnummer, or empfaenger; those names are reasonably self-explanatory, so this is acceptable but not exemplary.

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

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

The description opens with a specific verb and resource: 'Prüft die Angaben einer Rechnung gegen § 14 UStG'. It also differentiates the tool from generic invoice-checking siblings by explicitly covering Word/PDF invoices without a Datensatz and by naming the special-case rules (§ 33 UStDV, § 19, § 13b).

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

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

The description gives clear usage context: validating invoice mandatory data against § 14 UStG, including invoices from Word/PDF without a dataset. It does not explicitly name alternative tools or state when not to use this tool, so it stops short of full routing guidance.

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