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

With readOnlyHint=true already covering the safety profile, the description adds real value beyond annotations: price ranges are estimates marked approximate and must be presented as such, and 'Pro only' means the agent should recommend a shop rather than give repair instructions. It doesn't mention any result limits or missing-data behavior, so not a 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?

Four short sentences, front-loaded with the trigger condition, then the input hint, then the two output-presentation caveats. No filler and nothing that could be dropped without losing guidance.

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?

An output schema exists, so return values needn't be explained, and the description covers triggering, the optional input, and how to present estimates and 'Pro only' results. It doesn't note the implied dependency on resolve_vehicle for the slug parameters, though the schema descriptions do carry that.

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%, so the schema already documents year/make/model/mileage, making 3 the baseline. The description adds meaning the schema lacks by clarifying that mileage is optional and should be supplied only when the user mentioned it.

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 frames the tool around service intervals, what's due, and service cost, which makes its resource (maintenance schedule + price ranges) clear enough for an agent to select it. It stops short of a crisp verb+resource statement and never names sibling tools, so it is clear but not sibling-differentiated.

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?

It gives explicit triggering conditions ('when the user asks about service intervals, what's due, or what a service should cost') and a conditional input rule ('Pass mileage when known'). It also routes behavior for 'Pro only' jobs, but never states when NOT to use this tool or which sibling to prefer instead.

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