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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real value by naming the returned fields (Positionen, Status, offener Betrag, E-Rechnungs-Status), which matters since there is no output schema, but it says nothing about failure modes such as an unknown ID or access restrictions.

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?

One short sentence with the verb and resource front-loaded and zero filler. Slightly clipped as a fragment, but every word earns its place.

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 tool with annotations covering safety and a description that lists the returned fields, an agent has what it needs to call it correctly. Only the absence of guidance on obtaining the ID or handling not-found cases keeps it from a 5.

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% for the single 'id' parameter (Beleg-ID), so the schema already carries the semantics. The description adds nothing about the identifier's origin or format, which is the baseline-3 case.

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 (lesen) and resource (Beleg) and even enumerates what the read returns: line items, status, open amount, e-invoice status. That clearly separates it from list_documents or create_document, though no sibling is named explicitly.

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 gives no when-to-use guidance, no prerequisites, and no pointer to alternatives such as list_documents for discovering an ID. Usage is only inferable from the required 'id' parameter in the schema.

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