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

Annotations already establish readOnly/idempotent/destructive hints, so the bar is lower. The description adds behavioral detail beyond annotations by explaining the default nearest mode, the switch to station-history mode when an ICAO is provided, and what fields the observations contain. No contradictions with annotations.

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 compact, information-dense, and front-loaded with the core resource before moving to modes and examples. Every sentence earns its place and the two short examples make the schema concrete without bloat.

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?

With a 100%-covered schema, an output schema, and safety-relevant annotations, the description fills the remaining gap by explaining mode semantics and typical use cases. It is complete enough for an agent to invoke the tool correctly in either mode.

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 adds value by explaining how the parameters interact (nearest mode vs station mode) and by giving working examples for each mode, which helps an agent choose between location/station and n/hours. This goes beyond the individual parameter descriptions.

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 opens with a precise definition: METAR surface observations from weather stations, listing the data fields (temperature, wind, visibility, ceiling, flight category, raw METAR). It clearly distinguishes the tool's two modes and differentiates it from the many forecast/alerts siblings by anchoring on surface observations.

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 clear mode-selection guidance: nearest mode for closest N stations and station mode with hours for ICAO history, along with concrete JSON examples. It does not explicitly contrast the tool with sibling tools such as get_current_conditions, but the mode guidance is enough for correct usage.

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