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

With no annotations, the description carries the full burden and does substantial work: it discloses that `status` becomes `unavailable` when the forecast is over an hour old, that the data is a forecast rather than an observation, and that the MapMap gateway is required. It omits rate limits, caching, or failure modes beyond staleness, keeping it short of a 5.

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?

It is front-loaded with the resource identity, then layers return fields, caveats, and obligations. Every sentence carries information, though the mid-section mixing return-field documentation with caveats makes it slightly denser than ideal.

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?

An output schema exists, yet the description still adds useful value by explaining the aurora grid geometry (360x181 percent-per-pixel, column 0 at 180 W, row 0 at 90 N) and the staleness branch. Combined with the no-input declaration, attribution requirement, and forecast-not-observation warning, nothing an agent needs to call and interpret this tool is missing.

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 tool takes zero parameters, so per the rubric the baseline is 4. The description correctly states 'No input' rather than leaving the agent to infer it, and there are no parameter semantics left to clarify.

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 specific resources (the planetary Kp index and the NOAA SWPC OVATION aurora forecast) and a specific temporal scope ('right now'), making it immediately distinguishable from terrestrial-weather siblings like weather_along_route and weather_frames. An agent knows exactly what domain this serves without opening the schema.

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 gives clear situational context ('right now', a forecast 30-90 minutes ahead, not an observation) and instructs the agent on how to present results ('never present it as a sighting or a guarantee', 'Display the returned attribution'). It stops short of explicitly naming when to prefer a sibling tool or stating hard exclusions, so it is clear but not fully routing-aware.

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