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

No annotations exist, so the description carries the full burden. It usefully discloses that only DE is supported at present and encodes an actual validation rule ('steuersatz ODER steuerbefreiung_hinweis'), but it never states that the operation is non-mutating, what a check result looks like, or how findings are reported.

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?

Two tightly packed sentences with the scope constraint front-loaded and the required-field hint second; no filler. Slightly telegraphic phrasing ('Erwartet Felder wie') leaves the exact contract loose.

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?

Given no annotations, no output schema and a free-form nested object, the description covers the essential contract: what is checked, under which law, and which fields the object should carry. Only the missing coverage of 'land'/'verantwortlich' and the shape of the result keep it below full marks.

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 0%, so the schema says only that 'rechnung' is an open nested object. The description compensates by naming expected fields inside it (aussteller_name, rechnungsnummer, netto, steuersatz/steuerbefreiung_hinweis), which is genuine added meaning. It says nothing about the 'land' or 'verantwortlich' parameters.

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 states a specific verb and resource — 'Vorprüfung einer Rechnung auf Pflichtangaben' — and narrows scope to DE under § 14 Abs. 4 UStG, which is far more than the bare tool name conveys. It does not, however, differentiate itself from the sibling 'vat_pruefen', which an agent could plausibly confuse with this check.

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 word 'Vorprüfung' implies this is a pre-flight validation step, but there is no explicit statement of when to call it versus 'vat_pruefen', 'pflichten' or 'werbung_vorpruefen', and no exclusions. Usage must be inferred from the name and the legal reference.

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