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

Annotations already declare non-read-only, non-destructive, closed-world write behavior. The description adds two useful traits — immediate validation feedback and a JSON report return — but omits how the generated file is delivered (link, base64, attachment), whether the operation costs credits, and what the JSON report contains.

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 short, front-loaded sentences with no filler. Slight loss because the 'or ZUGFeRD PDF' phrasing conflates format options already enumerated in the schema and could mislead about XML-only output.

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?

The input side is thoroughly documented by the schema, but with no output schema and a complex nested payload, the description should say more about the returned JSON report and the generated document artifact. 'Returns a JSON report' is the only return-value information given.

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 coverage is 100% with detailed nested descriptions (UN/ECE units, VAT category rules, Leitweg-ID, date formats). The description itself contributes no parameter-level meaning, so the baseline 3 applies since the schema does all the work.

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?

States a concrete outcome: supplying invoice data yields a valid XRechnung or ZUGFeRD document that is validated. This clearly distinguishes it from siblings like validate-einvoice, einvoice-to-pdf, and extract-einvoice-xml, though the phrasing 'get a ... PDF' is slightly inaccurate since the xrechnung format returns XML only.

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?

No explicit when-to-use or when-not-to-use guidance, and no named alternatives. The agent must infer from sibling names whether to create here versus validate a pre-existing invoice or convert one to PDF; 'checked right away' only hints that validation may be bundled.

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