Current air quality at a place: PM2.5 and PM10 (µg/m³), US and European AQI, from Copernicus CAMS via Open-Meteo, with a signed receipt. Pass latitude and longitude, or a city. Costs $0.001 per call. The first 5 priced calls per caller are free.
| Name | Required | Description | Default |
|---|---|---|---|
| city | No | A city instead of coordinates, e.g. "Tokyo"; many spellings work (Токио, 東京). | |
| latitude | No | Latitude in degrees. | |
| longitude | No | Longitude in degrees. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full behavioral burden. It discloses external data source, current-value semantics, a signed receipt, per-call pricing, and a free-trial rule. It omits rate limits and error behavior, but the disclosed traits are meaningful and non-obvious.
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 tight sentences: result, input options, and cost. Information is front-loaded and no words are wasted.
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?
No output schema exists, so the description helpfully enumerates the returned metrics and units. It does not specify the exact response shape or behavior when neither city nor coordinates are given, but the core invocation contract is well covered.
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 the baseline is 3. The description reinforces the 'city or coordinates' choice but adds no significant meaning beyond what the schema already documents.
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 clearly states the tool's outcome: current air quality at a place, with specific metrics (PM2.5, PM10, US and European AQI). It also names the data source, which distinguishes it from weather_now and nearby_sensors even without explicit sibling comparison.
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?
The description gives explicit invocation guidance: pass latitude and longitude, or a city. It also adds cost and free-tier context that helps an agent decide when calling is appropriate. It does not explicitly name alternatives or exclusion conditions, but the intended use is clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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