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

The annotations already establish that this is a read-only, idempotent, open-world, non-destructive call. The description adds substantive behavior beyond that: the returned forecast fields, the uncertainty of hours and 1-2 Kp, the NOAA SWPC source, and a 1-credit cost.

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 front-loaded with the core question and then efficiently covers return fields, intended use, uncertainty, the observed-value alternative, and cost. Every sentence adds either selection guidance or behavioral context, with no redundant restatement of annotations.

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 no input parameters and no output schema, the description carries the burden of explaining what comes back and does so by naming the 3-hour blocks, daily maximum, peak block, and expected G-scale storms. It also provides uncertainty and cost context, leaving no material gap for calling the tool correctly.

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 no parameters, so there is no parameter semantics to explain; the baseline for a zero-parameter tool is 4. The description correctly focuses on output content and usage instead of inventing parameter guidance.

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 a specific forecast product — NOAA SWPC predicted Kp in 3-hour blocks over the next 3 days — and explicitly distinguishes it from the observed-value sibling kp_index_now. An agent can identify the resource, horizon, and returned elements 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 states the use case directly: planning aurora trips and checking storm watches. It also names kp_index_now as the alternative for observed values, which gives the agent a clear routing rule between forecast and current conditions.

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