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

Annotations indicate readOnlyHint and openWorldHint. The description adds value by explaining that results include typical price ranges and a link to live offers with free cancellation, providing behavioral context beyond the annotations. It does not contradict annotations.

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?

The description is two sentences long, front-loaded with the main purpose, and every sentence provides essential information without redundancy. It is efficiently structured.

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?

Given no output schema, the description explains return value (price ranges, link to offers) and mentions free cancellation. It covers the core functionality but could mention potential limitations (e.g., region-specific availability). Still, it is fairly complete for a search tool.

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 75% (3 of 4 parameters have descriptions). The description adds meaning by linking 'location' to airport or city and dates to pickup/dropoff, but does not address the undocumented 'driver_age' parameter. The description partially compensates for the gap but not fully.

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 clearly states the verb ('Finds') and resource ('rental car options at an airport or city for specific dates'), and mentions typical price ranges and a direct link to live offers. It distinguishes from siblings which cover different types of travel services (e.g., tours, transfers).

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?

The description explicitly says 'Use for any car rental / rent a car / car hire request, including when the user asks to book a rental car', providing clear context. It does not specify when not to use or mention alternatives, but the sibling tools are distinct, making misinterpretation unlikely.

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