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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context beyond these: it states the return shape ('chronological series of power percentages and status labels'), data coverage, and the auth/legal posture ('No auth — US NRC public domain data... unlimited free'). This aligns with and extends the annotations.

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 well-structured and front-loaded: it states the core action and scope first, then inputs, then output and use cases, then access constraints. Every sentence contributes useful information without excessive length.

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?

Given the small parameter count, rich input schema, output schema presence, and annotations, the description is complete. It covers what the tool returns, how to identify the reactor unit, the lookback window, the use cases, data coverage, and access restrictions. Nothing essential is missing for an agent to call it 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%, so the schema already documents both 'unit' and 'days' with examples and defaults. The description reinforces the parameter roles ('Provide the full NRC unit name... and the number of days to look back') but does not add significant new meaning beyond the schema.

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 opens with a specific verb and resource: 'Retrieve up to 365 days of daily power output history for a specific US nuclear reactor unit.' It also clarifies scope with 'Covers all units in the NRC 365-day rolling file,' which differentiates it from siblings like nrc.reactor.annual_data, nrc.reactor.current_status, and nrc.reactor.outages.

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 gives clear context for when to use the tool: 'trend analysis, outage detection, maintenance window identification, and capacity factor calculation for individual reactors.' It tells the user what inputs to provide, but it does not explicitly say when not to use it or name alternatives.

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