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

Annotations only declare the safe-read profile; the description adds substantial behavioral context beyond them — car origin (rental company vs private owner), instant:true immediate confirmation, similar_model class guarantees, the golden-link requirement, and explicit prohibitions on inventing phone numbers, addresses or licence plates, plus approximate coordinates. This is exactly the extra layer that annotations cannot carry.

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?

Organized into labelled blocks (CARS ON HOTELSCASA, PRICE, GOLDEN LINK RULE, NEVER) with the core purpose front-loaded. Dense but every block maps to a real decision the agent must make; slightly long, though nothing reads as filler.

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?

With an output schema present and annotations covering safety, the description supplies the remaining decision-critical detail: pricing edge cases, booking-confirmation semantics, link-mandate, and privacy constraints. An agent has everything needed to present and route a car 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 vehicle_id, lang, pickup_date and return_date are already documented in the schema. The description adds meaning to output fields (busy_ranges, price_day, price_note) rather than to the inputs, so it doesn't extend parameter semantics beyond the schema baseline.

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?

Opens with a specific verb+resource+scope: 'Full details of ONE rental car', then enumerates exactly what is returned (photos, specs, rental conditions, busy_ranges). The 'ONE' and the vehicle_id-by-search_vehicles linkage cleanly separate it from search_vehicles.

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 concrete operational guidance: use busy_ranges to propose alternative dates rather than declaring unavailability, and route price_day:null cars to booking_link via price_note. It never explicitly contrasts with siblings like check_vehicle_availability, but the usage context is clear enough to act on.

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