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

The annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so safety is covered; the description earns credit for adding a concrete cost disclosure ('2 credits') that annotations do not carry. It also states the payload content ('exact timestamps and reference timezones'), which helps the agent know what comes back. It does not discuss precision limits, timezone selection, or year-range constraints, keeping it below 5.

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?

Three short sentences with the core capability front-loaded, followed by output detail and cost. The opening 'Weather Seasons: Weather Seasons calculates...' redundantly repeats the title verbatim, which is the only real waste. Otherwise the content is tight and well ordered.

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 single-parameter, read-only lookup with an output schema present, the description covers purpose, return content, and cost adequately. It does not need to explain return structure since an output schema exists. The only missing piece is guidance on supported year ranges or accuracy for far-future/past dates, a minor gap for this complexity level.

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?

There is a single parameter with 100% schema description coverage, a default of 2025, and an example value, so the schema already carries the semantics. The description adds only the loose phrase 'any target year,' which does not clarify supported year ranges or whether astronomical calculations are valid for arbitrary historical/future years. Baseline 3 applies when the schema does the heavy lifting.

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 gives a specific verb and resource: 'calculates astronomical solstice and equinox dates for any target year,' and even names the four events covered (March/September equinoxes, June/December solstices). An agent can distinguish it from weather-forecast siblings like Weather or from SunriseSunset/MoonPhases. It falls short of 5 only because it never explicitly contrasts itself with those neighboring astronomy tools.

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?

There is no explicit when-to-use or when-not-to-use guidance and no named alternative. Usage is only implied by the phrase 'for any target year' and by the astronomy-specific framing, which suggests it is not a forecast tool. The agent must infer that this is for calendar/astronomy lookups rather than current weather.

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