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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful context beyond that: the full returned fields, the per-call cost of 10 credits, and a plan-gating note that the 7-day forecast requires a paid plan. It does not say what happens if neither city nor zip is supplied, which is a notable gap for a zero-required-param tool.

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 single dense sentence front-loads the core purpose and then layers output details and cost. It is somewhat long and mildly redundant, repeating the tool name in 'Weather: Weather is a current weather API', but every clause carries information an agent could use.

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 read-only annotations and an existing output schema, the return-shape burden is largely covered, and the description still summarizes the outputs, cost and forecast gating well. The remaining gap is behavioral edge cases: what happens with neither city nor zip provided, both provided, or an unknown location.

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 all three parameters are already documented, and the description only reinforces that city or zip code selects the location. The forecast discussion is actually slightly at odds with the schema, which says the forecast is included by default and can be disabled, whereas the description frames it as a paid-plan feature. Net added meaning over the schema is marginal.

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?

States a specific verb and resource: it is a current weather API that reports conditions for any city name or zip. It also enumerates exactly what is returned (temperature, wind speed and compass direction, metric and imperial units, coordinates, time zone, local time, day/night, UV risk), which implicitly separates it from adjacent siblings such as WeatherAlerts, MarineWeather and WeatherSeasons.

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 implied rather than stated: an agent can infer this is for current conditions at a location, and the 'Cost: 10 credits' note is useful for routing decisions. However, there is no explicit when-to-use or when-not guidance, no mention of how it differs from MarineWeather, WeatherAlerts or SunriseSunset, and no prerequisites.

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