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

Annotations already mark it read-only, idempotent, and non-destructive; the description goes further by disclosing exactly what is returned: header data, line items, totals, tax, discounts, payment status, dunning level, pause, original PDF flag, cancellation reason, project, and order. This is rich behavioral context beyond the structured annotations and is especially valuable because there is no output schema.

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 front-loaded with the core action and then uses a structured list of invoice elements, each earning its place by clarifying what will be returned. The closing sentence adds a meaningful usage contrast without redundancy.

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 a single required parameter, full schema description coverage, and safety annotations, the description is complete for the agent's invocation and expectation-setting. It enumerates the return contents thoroughly, compensating for the absence of an output schema, and no critical calling context is missing.

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% and the one parameter, rechnung_id, is already described as 'Die Kennung der Rechnung.' The description adds no additional meaning about the parameter's format or semantics, 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 opens with the verb 'Zeigt' and a specific resource, 'eine einzelne Rechnung vollständig', immediately establishing the tool's purpose. The long enumeration of fields makes it unmistakably a detail-view tool and distinguishes it from sibling tools like rechnungen_suchen or rechnung_versenden.

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 clearly implies the tool is for full inspection of one invoice ('einzelne Rechnung vollständig') and adds the purpose statement 'prüfen, WAS auf der Rechnung steht — nicht nur, wie viel.' It does not explicitly name alternatives or exclusions, but the context is unambiguous enough for an agent to select it over search or mutation siblings.

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