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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description adds real context beyond them — provenance (multi-year data vs curated research seasons), confidence and caveats in the result, and a metering note ("metered, free during early access"). That cost/paywall disclosure is exactly what annotations cannot convey.

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 front-loaded sentences: what it ranks, what the output provenance is, then the operational note. No filler, and the most decision-relevant framing ("one thing at one place") comes first.

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?

Output schema exists, so return values need not be described, and the description still flags confidence/caveats and data source. The one omission is how location is resolved when only `for` is supplied, since area/spot/lat-lon are all optional — an agent gets no hint about precedence among those four location inputs.

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 coverage is 100%, so every parameter including `for` examples, lat/lon 50 km resolution, area/spot ids, and the limit default is already documented. The description only reinforces the constraint that both the subject and the place are singular per call; it adds no new syntax or resolution detail.

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 ("ranks the calendar months") plus the exact scope — one thing at one place — and enumerates the three kinds of inputs accepted. It separates itself from best_day by making the month granularity explicit, but never names a sibling for direct routing.

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?

"A decision call" implies this is the tool for planning-oriented questions, but there is no explicit when-to-use versus best_day, get_conditions, or get_seasonality. The agent must infer the boundary from the word "months" alone.

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