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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed world, so safety is covered. The description adds real behavioral context beyond that: the two distinct legal deadlines, the conditional behavior tied to received_on, and the accepted date formats, though it says nothing about how the result is returned.

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?

Front-loaded with the primary calculation and its statutory basis, then the conditional case, then the format note. The parenthetical English gloss is slightly redundant for a German-domain tool but is efficient and aids disambiguation, so the text stays tight.

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 pure calculator with no output schema, the description conveys the inputs, the conditional logic, and the statutory rules that determine the result. It could be stronger by sketching the returned values (e.g., both computed dates and whether the objection deadline applies), but it is otherwise sufficient to invoke correctly.

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%, so baseline is 3, but the description adds meaning the schema does not: it states both accepted date formats (JJJJ-MM-TT or TT.MM.JJJJ) and ties each parameter to the specific deadline it drives via the statutory periods.

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 verb (calculates) and resource (the landlord's Abrechnungsfrist and, conditionally, the tenant's Einwendungsfrist under § 556 BGB), which is unmistakable and clearly distinct from the sibling lookup tools. The legal citations and the conditional on received_on make the scope precise.

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?

It implicitly scopes usage to German Nebenkostenabrechnung deadlines and explains the condition under which the second computation occurs ('wenn das Zugangsdatum bekannt ist'), which tells the agent when the optional parameter matters. No explicit exclusions or alternatives are named, but no sibling overlaps this calculation.

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