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

With no annotations provided, the description carries the full burden. It states a read-only parsing action and mentions returning data, but it does not disclose edge-case behavior such as what happens if the PDF lacks embedded XML, whether the tool supports all versions of the formats, or any error handling. It provides basic transparency but lacks deeper behavioral context.

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?

The description is a single sentence that efficiently conveys the tool's purpose and output. It is front-loaded with the key verb and object, with no redundant or filler content. Every phrase contributes useful information.

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 the tool's narrow scope and the schema covering both parameters, the description is mostly complete. It explains the input format and the nature of the output (structured invoice data). However, it does not specify the exact response structure or failure modes, which would be useful since there is no output schema. Overall, it is adequate for selection and 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 100%, with both parameters (pdf_path and pdf_base64) already documented as alternatives for providing the PDF. The description adds no extra parameter-specific semantics beyond what the schema provides, so the baseline score of 3 is appropriate.

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 clearly states the tool's function: parsing ZUGFeRD or XRechnung XML embedded in PDFs. It specifies the input (PDF with embedded machine-readable XML) and the output (structured invoice data), distinguishing it from sibling tools like invoice_ocr or invoice_parse_text that handle other formats.

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 implies when to use the tool: when the PDF contains ZUGFeRD or XRechnung embedded XML. It does not explicitly list alternatives or exclusions, but the mention of 'machine-readable format' provides clear context. Given the sibling tools (e.g., invoice_ocr, invoice_parse_text), the use case is understood.

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