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

Annotations already cover read-only/idempotent/open-world safety, and the description goes well beyond them: data provenance (CAMS Copernicus via Open-Meteo, CC BY 4.0), no API key required, honest disclosure of geographic and seasonal data gaps, and the units/level format returned. These are exactly the facts an agent needs to set user expectations about data availability.

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 capability and coverage constraints, then cleanly labeled "Use when", "Example" and "Data" blocks. The dense parenthetical pollutant lists are information-bearing rather than padding, and every sentence carries either scope, trigger or provenance.

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 no output schema, the description still enumerates the returned quantities and units, notes the forecast horizon, discloses coverage limits, and cites the data source. Nothing material is missing for an agent to call this correctly and interpret the result.

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 location, lat/lon, days and lang are already documented, and the baseline of 3 applies. The description reinforces that days means daily maximums over up to 4 days and supplies a concrete example payload, but it adds nothing about the lat/lon alternative or language handling.

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 resource (pollen and air quality forecasts) and enumerates exactly what is measured (birch, alder, olive, grass, mugwort, ragweed in grains/m³; European and US AQI, PM2.5, PM10, ozone, NO2). The forecast horizon (now + up to 4 days) and regional scope (air quality worldwide, pollen Europe-only) cleanly separate it from siblings sun_times and weather_forecast.

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?

An explicit "Use when" clause lists concrete triggers (hay fever, allergy, smog, asthma, outdoor sport) plus example phrasings, which is far more than most definitions offer. It also states the important when-not condition for pollen (Europe only, in season). No routing to sibling tools is given, keeping it short of a 5.

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