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

Annotations already cover readOnly/idempotent/openWorld, so the bar is lower; the description adds genuinely new context by stating values are pre-computed over a full snapshot history, that no raw timeseries is returned, and the specific ~2 week / ~2 month windows. This is helpful disclosure about the nature of the result set.

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-loaded with the core purpose, then the metric enumeration and the caveat about pre-computation. It is a dense paragraph but every clause carries selection-relevant detail; slight redundancy in restating return fields that the output schema already defines.

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 an output schema present, the description need not document return values, yet it does so anyway while also covering scope, computation semantics, and the embedded web URL. An agent has everything needed to call this 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% with a single param whose schema text already explains it is the UUID returned by `devices`. The description reinforces but does not extend this (no format examples or error behavior), 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 ('Return aggregated battery metrics for ONE specific device') and enumerates the exact metrics returned (temperature avg/min/max, battery level, charge/discharge times, awake ratio). The emphasis on 'ONE specific device' clearly separates it from fleet_summary and model_summary siblings.

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 scope statement ('ONE specific device') gives a clear condition for selecting this over fleet-level siblings, and the required device_uid from the `devices` tool implies the prerequisite lookup step. It stops short of explicitly naming fleet_summary/model_summary as the alternatives for multi-device aggregation.

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