Background air pollution at an AEMET EMEP/VAG rural station

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

With no annotations, the description carries the behavioral burden, and it does so well by explaining that the tool returns only the latest reading, covers rural baseline pollution, and intentionally excludes urban measurements. It could additionally state output format or freshness guarantees, but the core behavioral boundary is clearly disclosed.

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?

The description is front-loaded with the core action and resource, then adds a necessary background clarification and a strong use-caveat. It is slightly verbose, but every sentence contributes meaningful selection and misuse-avoidance information.

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?

The description covers purpose, scope, and limitations well, but it does not state what happens when neither 'station' nor 'location' is provided, even though both parameters are optional. With no output schema, the absence of a clearer return-structure description also leaves some ambiguity for the agent.

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 itself adds little parameter-specific meaning beyond what the schema already provides. The schema already documents station precedence and the nearest-station behavior for location, so the description does not need to compensate.

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 names a specific verb ('Returns'), a precise resource ('AEMET's background pollution network'), and the scope ('13 rural reference stations... O3, NO, NO2, SO2 and PM10'). It clearly distinguishes the tool from urban air-quality expectations and from sibling forecast/observation tools.

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 explicitly states this tool is for BACKGROUND pollution and tells the agent when NOT to use it: 'It does NOT answer how is the air in Madrid/Barcelona today'. It also directs urban air-quality queries to city/regional networks, preventing misuse as a proxy.

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