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

The description discloses data sources, update frequency ('daily'), historical depth ('history to 1966'), and output fields (score, trend, confidence, top_drivers). The readOnlyHint annotation already signals safety, and the description adds context about how data is derived without contradicting the annotation. It does not mention potential limitations or error conditions, but for a read-only tool this is sufficient.

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 two sentences, front-loaded with the core output and data sources, followed by explicit use cases. Every sentence carries meaningful information and there is no fluff or repetition of schema fields.

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 there is no output schema, the description lists the returned fields (score, trend, confidence, top_drivers) and explains the underlying methodology. It covers the main purpose, use cases, and update cadence. The parameter is fully documented in the schema, so the description is complete for an agent to select and invoke 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?

The schema has full 100% documentation for the single 'days' parameter, so the baseline is 3. The description does not elaborate on parameter behavior, but it mentions 'daily, history to 1966' which implicitly aligns with the optional history series. The schema itself already explains the Gold tier requirement and the range (1-1825), so the description adds no extra parameter semantics.

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 uses a specific verb 'Returns' and clearly names the resource ('regional sunlight-deficit wellbeing risk score'), including its scale (0-100) and core components (NSRDB solar irradiance, NOAA daylight duration, mental-health utilization). This distinguishes it from generic health risk tools and sibling tools, which are simply numbered without titles.

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 explicitly states when to use the tool: 'Call when the user asks about seasonal affective risk, winter light deprivation, or regional mental-health demand, or when timing employer wellness campaigns, EAP outreach, or telehealth staffing by region.' It provides clear contexts but does not mention when not to use it or alternatives, so it falls just short of a perfect score.

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