rain_thresholds

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

Annotations already establish readOnly/idempotent/closed-world, and the description adds a genuinely important behavioral caveat: values reflect the ~25 km ERA5 grid cell including surrounding mountains, not valley-floor gauge readings. It also discloses the 35-year record basis. It does not cover return format, but annotations lower the bar on that.

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?

Front-loaded with the core definition, then the CRS/grid caveat, then the usage warning. Three tight sentences with no filler, though the colloquial 'in town' phrasing is slightly imprecise for a global tool.

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?

An output schema exists, so return values need not be explained, and the description covers scope, derivation window, and the grid-vs-gauge caveat well. The only real gap is the ambiguity of the single required 'station' argument.

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 one parameter ('station') with 0% schema description coverage, and the description never says what identifier form it expects or where valid values come from (e.g., list_stations). With low coverage, the description was the place to compensate, and it does not.

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 states a specific resource and what it returns: percentiles of daily rain defining heavy/extreme/rare days, derived from a 35-year station record. That is far more informative than the bare name, but it does not explicitly distinguish itself from siblings like get_daily_weather, so the agent must infer the boundary.

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?

It gives clear intended use ('use them to judge how unusual a day is') and an explicit when-not ('not how much fell in town'), which steers the agent away from misusing thresholds as rainfall totals. It stops short of naming an alternative tool for actual amounts, so it is not fully prescriptive.

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