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

With no annotations provided, the description carries the full burden. It meaningfully discloses behavior: returns a ranked comparison by pollutant, includes DAQI bands and distance to nearest monitor, and imposes a 2–6 location constraint. It does not mention side effects or error handling, but as a read-only comparison tool, this is acceptable and the description goes beyond a mere tautology.

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 and well-structured: it front-loads the main purpose, then the output, then use cases, and finally parameter details. Every sentence earns its place with no redundancy. The use of a short 'Args' section cleanly separates parameter semantics without bloating the main description.

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?

Given the tool's moderate complexity (2 parameters, no output schema, no annotations), the description covers all essential aspects: purpose, output shape, use cases, and parameter format/constraints. It provides enough detail for an agent to select and invoke the tool correctly, even without an output schema.

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 0%, so the description compensates exceptionally well. It explains the locations parameter format ('postcodes, place names, or "lat,lon"') and the 2–6 item constraint, and clarifies the pollutants parameter as optional with an example and default behavior. This adds substantial meaning beyond the bare schema.

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 a specific action ('Compare current air quality') and resource ('across multiple locations side-by-side'), distinguishing it from siblings like get_current_aq which likely handles a single location. It also mentions the key output (ranked comparison by pollutant with DAQI bands), leaving no ambiguity about the tool's purpose.

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 provides explicit use case contexts ('comparing development sites, school locations, or residential options'), giving clear guidance on when to use this tool. It does not name alternative tools or state when not to use it, but the use case framing is sufficiently clear and implies comparison scenarios as opposed to single-location queries.

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