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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral facts: a short cache layer and the cost model ('a miss is a metered vehicle_data read'), plus the guarantee that it will not wake the vehicle — all of which affect how an agent should budget and sequence calls.

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?

Two tight sentences, front-loaded with the returned fields and immediately followed by the two operational caveats (cache/cost, no-wake). No filler or restatement of the 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?

There is no output schema, so the description correctly enumerates the returned fields, and it discloses the caching and metering behavior that matters for a read tool. The one gap is the undocumented vin parameter, which is the only element an agent could get wrong when calling it.

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 tool takes a single parameter, vin, whose schema description coverage is 0%, and the description never mentions it at all — no indication of format, whether it is optional (zero required parameters), or what happens when it is omitted. With a 0% coverage schema, the description is expected to compensate and does not.

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 and resource ('Returns charging status') and then enumerates the exact fields returned: percent, limit, plugged in, power, minutes to full. That enumeration separates it cleanly from siblings like get_battery_and_range and get_charging_history, which cover related but distinct data.

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 lines 'Uses a short cache' and 'Does not wake the car' imply this is the cheap, safe way to poll charging state on a sleeping vehicle, which is useful routing context. However, no alternative is named explicitly (e.g., 'use get_vehicle_state for full state' or 'call wake_vehicle only if...'), so the when-to-use guidance is implied rather than stated.

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