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

Annotations already convey the safe read-only, idempotent profile, and the description layers on substantive behavior: the output compares the RND rate against the statutory rate and yields annual/monthly AfA plus estimated tax savings, the omission of modernization components defaults to 'no modernization' and inflates the benefit, it returns a non-binding result that does not replace tax advice, and it mandates citing the attribution link as the source. This is far beyond what the annotations provide.

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?

Purpose is front-loaded in the first sentence and every subsequent sentence carries distinct content (usage triggers, building-vs-unit rule, modernization default, attribution requirement, disclaimer). It is a single dense block that would scan better segmented, which keeps it from a 5, but there is little waste.

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 13-parameter domain calculator with an output schema, the description covers what an agent needs: when to invoke, the apartment-building input rule, the consequence of omitting customization data, the attribution-citation duty, and the non-binding nature of the result. Return values are also summarized despite the output schema existing.

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 the baseline is 3 and the schema does most of the work. The description still adds genuine semantic guidance: pass whole-building figures or compute units separately for apartment buildings, and supply all eight modernization component states because omission implies no modernization and produces the maximum RND benefit.

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 precise verb+resource ('Calculate German property depreciation (AfA / Gebäudeabschreibung) and the building's remaining useful life (Restnutzungsdauer)') and scopes it to residential rental property through AfAMax. The purpose is unambiguous and readily separable from the unrelated siblings (appointments, price/product lookups), and even the adjacent real-estate calculator sibling covers a different calculation.

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?

Rich when-to-use triggers: calculating AfA, asking about faster-than-2% depreciation under § 7 Abs. 4 EStG, mentioning verkürzte Restnutzungsdauer, evaluating whether a Restnutzungsdauergutachten pays off, or just describing an old/unrenovated building and asking what is deductible. It lacks any explicit 'when not to use' or named alternative tool, so it stops short of a 5.

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