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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior, so the description does not need to restate those. It adds meaningful behavioral context: the ranking reflects current conditions ('right now'), covers exactly 338 CNEMC-monitored prefecture-level cities, and supports ranking by a specific pollutant. This goes beyond the structured annotations and helps an agent understand scope and freshness.

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 concise yet information-dense: it states the core ranking function, gives three illustrative user questions, mentions optional pollutant ranking, and specifies geographic coverage, all in two sentences. The most important distinguishing facts are front-loaded, and there is no redundant repetition of annotation or schema details.

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 read-only ranking tool with zero required parameters and full schema coverage, the description provides sufficient context to call it correctly. It clarifies scope, ranking polarity, optional pollutant filter, and answerable question types. With no output schema, a brief note on the exact returned fields could make it more complete, but this is not a significant gap for selecting and invoking the tool.

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?

The input schema already provides complete descriptions for all three parameters, with enum constraints and defaults, so the description's parameter-related additions are minimal. It does reinforce that 'pollutant' overrides overall AQI ranking and gives example query patterns, but this largely mirrors schema content. A baseline of 3 is appropriate given full schema coverage.

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 identifies the tool as a nationwide ranking of Chinese cities by air quality, with explicit example queries and a note about optional pollutant-based ranking. It distinguishes itself from sibling tools like china_air_quality by emphasizing the ranking over all 338 monitored cities rather than single-city conditions.

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 strong contextual cues for when to use it: questions about cleanest or most polluted cities, optional pollutant-specific rankings, and coverage of all CNEMC-monitored cities. It does not explicitly name sibling tools to avoid (e.g., china_air_quality for a single city), but the intended use case is clear enough for an agent to select this tool appropriately.

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