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

Annotations provide readOnlyHint=true, and the description adds useful context beyond that: it explains the score is a daily composite z-score using Kp peak/mean/trend, notes a 10-year history, and states updates are daily. This gives a richer behavioral picture without contradicting 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 concise sentences: output definition, usage triggers, and update frequency. Every sentence adds value, no redundancy, and the most important information is front-loaded.

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?

Without an output schema, the description covers return fields (score, percentile, trend, methodology_version) and gives a clear risk scale. It does not explain what percentile or trend mean in detail, but for a simple read-only tool with one optional parameter, it 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?

Schema description coverage is 100%, with the 'days' parameter thoroughly documented in the schema (optional history series, up to 5 years, Gold tier requirement, fallback to snapshot). The tool description itself adds no extra parameter context, but the schema carries the full burden well.

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 states exactly what the tool does: returns a 0-100 geomagnetic activity risk score based on NOAA SWPC Kp data, with output fields listed. It is highly specific and clearly distinct from generic siblings, covering the domain thoroughly.

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 explicitly lists when to call the tool (user asks about space weather, geomagnetic storms, Kp index, etc., or for satellite/GNSS/HF operations). It lacks when-not-to-use guidance or named alternatives, so it stops short of a full 5.

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