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

Beyond the readOnly/idempotent annotations, the description discloses three operational traits an agent could not infer: results come from a short cache, a cache miss triggers a metered (billable) vehicle_data read, and the call does not wake a sleeping car. Those are exactly the cost and side-effect facts that drive tool selection here.

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?

Three short sentences, front-loaded with what is returned, then the caching behavior, then the no-wake guarantee. No filler and nothing repeated from the annotations or title.

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 usefully enumerates the returned fields, and it covers the cost/side-effect profile that annotations do not. The one gap is input handling — it says nothing about the required VIN or default-vehicle behavior for a one-parameter call.

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?

The single parameter 'vin' has zero schema description coverage and is not optional-annotated, yet the description never mentions it — not what a VIN looks like, not whether it can be omitted for a default vehicle, not whether failure occurs without one. With one undocumented parameter, the description fails to compensate for the coverage gap.

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 names the exact returned fields (battery percent, rated range, charge limit, charging state), so the agent knows precisely what this retrieves. It implicitly separates itself from a full vehicle_data fetch by describing the cached fast path, but no sibling is named explicitly.

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 cost framing ('short cache', 'metered vehicle_data read') implies this is the cheap way to check battery, which is useful guidance against get_vehicle_state. However, it never states when to prefer this versus get_charging_status or get_vehicle_state, nor any precondition such as the vehicle needing to be online.

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