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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: the specific data returned (APK defect rate vs. average, top 10 defects, recalls with component and risk, open-recall share, odometer rollback share, registrations) and the ~450-model coverage scope.

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 'Free' and the trigger condition before the dense data enumeration. The long list of returned fields is information-dense rather than padded, though it is packed into a single sprawling sentence.

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 no output schema, the description carries the burden of describing return contents, and it does so thoroughly. For a simple two-parameter lookup tool, an agent has enough to invoke and interpret 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 description coverage is 100% and both parameters (make, model) are documented in the schema with examples. The description adds no syntax, format, or matching guidance beyond what the schema already provides, so the 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+resource: reliability facts for a car model in the Netherlands sourced from RDW data. The 'Free' prefix implicitly distinguishes it from the paid sibling buy_full_vehicle_report, though it never names that sibling directly.

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 trigger conditions ('when the user asks how reliable a car model is, or which used car to buy'), which is clear usage context. It stops short of naming when NOT to use it or pointing to a specific alternative tool.

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