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

Annotations already declare readOnlyHint, idempotentHint and a closed-world profile, so the safety bar is low. The description adds genuine value by disclosing the output dimensions (kWh and cost per day, month and year), which is not covered by any schema. It still omits details like rounding or currency handling, so it is good but not exhaustive.

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 plus a link; the concrete example is front-loaded and immediately conveys the computation. The URL and marketing-flavored example consume some space that could carry behavioral detail, but there is little waste overall.

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 six all-optional parameters, full schema coverage, and no output schema, the description does the important extra work of naming the outputs (kWh, daily/monthly/yearly cost). The only residual gap is the preset enum's behavior, which the schema already labels as 'Appliance.' Adequate to call the tool 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 coverage is 100%, so the baseline is 3. The description exceeds that by giving a concrete instantiation ('100 W TV on 5 hours a day ... at 17¢/kWh') that maps directly onto the watts, hours and price parameters and their units, reinforcing their meaning. It adds modest but real semantic value.

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 states a specific verb and resource: turning an appliance's watts and hours into kWh and running cost by day, month and year. This clearly distinguishes it from most siblings (e.g., fuel_cost_calculator covers a different resource), though it never explicitly names a sibling to contrast with. Purpose is unambiguous to an agent.

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?

Usage is only implied through the worked example and the phrase 'any appliance's watts and hours of use.' There is no explicit when-to-use, when-not, or alternative-tool guidance. For a standalone calculator the context is inferable, but nothing routes the agent explicitly.

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