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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds useful beyond-annotation behavior: the return is a base64-encoded file, and E-Rechnung PDFs include embedded XML. It does not mention error cases, permissions, or size limits.

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 sentences, front-loaded with the action and resource, then the return-format detail. No redundant or wasted text.

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 single-parameter read/download tool with annotations and no output schema, the description covers the key return-format detail (base64) and the E-Rechnung XML nuance. The main missing piece is explicit routing to the sibling XML-download tool.

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?

There is only one parameter ('id', Beleg-ID) and schema description coverage is 100%, so the schema already documents it fully. The description adds no additional meaning about the ID format or source, which is an acceptable baseline given complete schema coverage.

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 specific verb and resource ('PDF eines Belegs herunterladen') and adds the scope detail that E-Rechnung PDFs contain embedded XML. This implicitly distinguishes it from the sibling download_e_invoice_xml, though it never names that alternative directly.

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 parenthetical about E-Rechnung with embedded XML hints at when this tool is appropriate, but it does not explicitly say when to use it versus download_e_invoice_xml or get_document. Usage is only implied, not stated.

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