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

Annotations already cover read-only, idempotent, non-destructive and closed-world behavior, so the description's job is to add approximation semantics — which it does by flagging notary/land register as 'a usual range' and adding an 'estimate, not tax or legal advice' disclaimer. It still doesn't say what happens when no price or listing_id is supplied (all five parameters are optional).

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-loads what is calculated before explaining inputs, and each sentence carries information. The input-routing sentence is slightly dense but not padded.

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?

An output schema exists so return values need no explanation, annotations carry the safety profile, and the description covers scope, component assumptions and the two valid input paths. Enough for an agent to invoke it 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 coverage is 100%, so every parameter already carries its own description including the plz-derives-state fallback and the commission percentage bounds. The description restates the listing_id-to-price/state/commission linkage rather than adding new syntax or constraint detail, so baseline 3 applies.

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 and resource ('estimates the additional costs of buying a property in Germany') and enumerates the cost components covered: transfer tax, notary/land register, and buyer's commission. This clearly separates it from siblings like calculate_affordable_price or compare_listings.

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?

Gives explicit input routing: pass a listing_id from search_listings to inherit price, postal code and commission, or alternatively pass price and state. It names the sibling tool to source the ID from, though it never states when to prefer this over calculate_affordable_price or what to do if neither input path is available.

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