Geomagnetic K-index (NOAA SWPC)

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

Annotations already declare readOnlyHint and idempotentHint, indicating safe, idempotent reads. The description adds value by explaining the rolling window behavior (window_max always scanned regardless of points) and the return structure (latest, window_max, recent observations). 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?

Three sentences, front-loaded with the main purpose. Every sentence contributes unique information: the primary output, the window_max detail, the observation count, and the data source. No redundancy or filler.

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 simple read tool with an output schema (present but not shown), the description covers what is returned, the window behavior, and the source. It lacks an explanation of the G1-G5 scale, but that is likely common knowledge or detailed in the output schema. The description is largely 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?

The input schema provides 100% coverage for the single parameter `points` with a description. The description adds critical context: the full 6-hour window is always scanned for window_max regardless of the points value, clarifying that points only affects the number of returned observations, not the max computation.

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 the tool provides the current planetary K-index with G1-G5 storm severity classification, along with the maximum K-index in a rolling 6-hour window and recent observations. It explicitly names the resource (K-index) and differentiates from sibling space.swpc tools (aurora, solar regions, solar wind) by its specific subject matter.

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 implies usage for geomagnetic activity monitoring but does not explicitly state when to use this tool versus alternatives like space.swpc.aurora or space.swpc.solar_regions. No 'when-to-use' or 'when-not-to-use' guidance is provided.

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