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

Annotations already mark the operation as read-only and non-destructive. The description adds useful behavioral context by stating that the response includes the letter, its associated order, and a PDF download URL that is only valid for 24 hours. It does not cover error cases, but that is acceptable for a simple read-only retrieval.

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 short, front-loaded with the main verb and resource, and includes the important URL-expiry detail at the end. The main inefficiency is repeating the same content in German and English, but overall it is compact and readable.

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 description covers the main return values and the time-limited URL, which is useful since there is no output schema. However, it does not explain the optional `reasoning` parameter or how the agent should obtain/use the IDs, leaving the invocation details partially dependent on inference.

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 description needed to explain the parameters, but it never mentions orderId, letterId, or reasoning. The parameter names are somewhat self-explanatory, yet the purpose of `reasoning` and whether both IDs are required or how they relate remain unclear.

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 action ('Returns/Liefert') and a specific resource: one of the partner's letters, together with its order and a 24-hour-valid PDF download URL. This makes the tool's core purpose clear and implicitly distinguishes it from list/search tools, though it never explicitly names a sibling.

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 the tool is for retrieving a single letter when its IDs are available, but it does not explicitly say when to use this tool instead of letter_list, letter_search, or letter_preview. It provides no when-not-to-use guidance or alternative routing.

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