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

With no annotations, the description carries the full burden, and it does disclose two real behavioral facts: the 400 km radius ceiling and the threshold-based filtering of results. It does not say what happens when no station meets the threshold, whether results are sorted by distance or reading, or that a subscriber token is required for access (that lives only in the schema). Useful but incomplete for an unannotated tool.

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?

A single dense sentence with zero filler, and the tier gate plus the geographic scope are front-loaded. Every clause contributes a distinct fact (tier, stations, radius, origin, threshold).

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?

For a 4-parameter tool with no annotations and no output schema, the description covers the filtering semantics but omits defaults for min_aqhi and radius_km, the auth requirement, and any hint of the return shape. Adequate to call correctly in the common case, but not complete.

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 only 25%, so the description must compensate, and it largely does: it explains that the radius is in km with a max of 400, that the postal code is the origin point, and that min_aqhi acts as a readings threshold. Only the meaning of 'readings' relative to min_aqhi and any defaults remain unstated.

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 concrete resource set (AQHI stations), a spatial scoping mechanism (within a radius of a postal code) and a filter (readings at or above a threshold). An agent can tell this is a proximity-based air-quality query, distinct from a forecast tool like aqhi_forecast. It stops short of naming the siblings it should be preferred over, so it is clear but not differentiated.

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 only usage signal is the leading 'PRO.', which implies a paid-tier gate, and the inline 'max 400' cap. There is no statement of when to choose this over air_quality, sites_check, or aqhi_forecast, and no prerequisites beyond the implicit subscription. An agent must guess the selection criteria.

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