Availability Check

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=true, covering the safety and world-view. The description adds useful behavioral context beyond those: it specifies the input format (car slug or VIN, YYYY-MM-DD dates) and clarifies that 'end = return day'. This goes beyond what the schema or annotations provide, though it doesn't discuss edge cases like timezone or inclusivity of dates.

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 extremely concise—two sentences—and front-loads the core purpose. The parameter explanation is compactly packed into a single line using separators (·). Every sentence earns its place with no redundancy or 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?

For a simple availability check with an output schema, the description covers the essential semantics and parameter meanings. It might be improved by noting whether the result is a boolean or includes availability windows, but the output schema likely handles that. Minor gaps like timezone assumptions or inclusive/exclusive date boundaries are not addressed, but these are not critical for the tool's core function.

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 0%, so the description carries the full burden of explaining parameters. It does so completely: 'car' is identified as a slug or 17-char VIN, and 'start'/'end' are YYYY-MM-DD dates with the note that 'end = return day'. Every parameter is explained with both format and meaning, fully compensating for the bare schema.

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 uses a specific verb ('Check') and clearly states the resource ('whether a car is free for a date window'). It distinguishes itself from siblings like fleet_list (listing) and quote_trip (pricing) by focusing on availability, so an agent can select it correctly without ambiguity.

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 clearly implies the use case (checking availability), but it does not explicitly state when to use this tool versus alternatives, nor does it mention any exclusions or prerequisites. The agent must infer that this is the go-to tool for availability checks based on the purpose alone.

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