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 genuinely new behavioral context by specifying that the price is the exact total in EUR and already includes VAT and climate levy, and that the response indicates the payment method. It does not say how unavailability is signalled, which keeps it below 5.

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 tightly constructed sentence that front-loads the core outcome (free apartments + exact price) and ends with the prerequisite call. No filler, no redundancy with the title.

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?

No output schema exists, so the description must convey return content, and it does identify the three key results (available apartments, total price, payment method). It is not fully complete for an availability check — nothing about what happens when no apartments are free or how the result is structured — but the essentials an agent needs are present.

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% — all three parameters have descriptions including the guest default and the check_out-after-check_in constraint. The description adds no additional semantics about dates or guest counts (e.g. capacity effects), so the schema does the work and 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 (check which apartments are free for given dates) plus the exact payload returned: total price in EUR with VAT and climate levy, and how the guest would pay. This is far more than a restatement of the name and clearly separates price/availability checking from the booking action.

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?

Explicit sequencing rule: "Always call this before book_stay" tells the agent exactly when this tool is mandatory relative to a named sibling. It stops short of saying when to use it versus list_apartments or get_property_info, so it is clear but not a complete decision tree.

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