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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is known. The description adds behavior beyond annotations: data update schedule (M–F, previous day's capacity), the approximate number of units (~95), and the auth/free nature ('No auth — US NRC public domain data'). It also specifies the output fields. This adds meaningful context without contradicting annotations, though it could detail response size or pagination, which is minor given the small scope.

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?

The description is a single, well-organized paragraph that front-loads the core purpose and then elaborates on output, data freshness, use cases, and licensing. It is concise and avoids redundancy, though the marketing sentence about 'essential for...' could be trimmed to improve tightness. Overall, it is appropriately sized and readable.

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?

For a simple read-only tool with one optional parameter and an output schema, the description covers what is needed: purpose, output fields, update timing, auth, and typical use cases. It does not explain return value formatting, but the output schema handles that. It could mention potential caveats (e.g., how 'shutdown' is defined), but these are minor. The description is complete enough for correct invocation.

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 input schema has one parameter (sort_by) with a full description of each enum value, achieving 100% schema description coverage. The description adds no additional parameter semantics beyond what the schema provides, which is acceptable. With high schema coverage, the baseline of 3 applies, and the description does not compensate with extra info, so a 3 is appropriate.

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 (Get), resource (latest daily power output for all ~95 US commercial nuclear reactor units), and explicitly lists the returned fields (power level %, operational status, fleet-wide summary counts). This clearly differentiates it from siblings like nrc.reactor.history, annual_data, or outages by focusing on current status. The purpose is unambiguous and specific.

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 description provides clear usage context ('Essential for US energy grid monitoring, nuclear generation capacity dashboards, and power market analysis') and notes the update frequency (each business day M–F, reflecting previous day's capacity). However, it does not explicitly mention when not to use this tool or point to sibling alternatives for historical data or outages. Since the name itself distinguishes it from siblings, the guidance is adequate but lacks explicit exclusions.

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