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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered structurally. The description adds genuinely new behavioral context beyond the annotations: the data is cached, the horizon is 48 hours, and the response includes the time the grid was produced. It does not, however, say how stale the cache may be or what format the coverage/timestamp report takes.

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?

One short sentence with no padding, and the key qualifiers (cached, 10 m wind/rain, 48 hours) come first. It is grammatically a fragment rather than a declarative statement of what the tool returns, which slightly hurts agent parsing.

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 zero parameters, no output schema and annotation coverage of the safety profile, the description covers the essentials. It still leaves the actual return shape unstated — whether 'coverage' means geographic bounds, variable list, or resolution — which an agent would need to know before relying on it.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline is 4. The description's mention of a 48-hour horizon and cache timestamp clarifies the fixed scope, which is the only parameter-like information available.

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 identifies a specific resource — the cached 10 m wind and rain grid covering the next 48 hours — and states that it reports coverage and generation time rather than the data itself. The verb is implicit (a noun-clause fragment rather than 'Returns...'), and it does not distinguish itself from siblings like cell_weather_point or cell_weather_clouds, but an agent can still tell what the tool is for.

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 guidance on when to call this versus the weather siblings (cell_weather_point, cell_weather_clouds), no statement of prerequisites, and no indication of what an agent should do with the result. Usage must be inferred entirely from the resource name.

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