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

Beyond the annotations, the description discloses the data source (NOAA SWPC), the 1-credit cost, the returned fields, and the important behavioral limit that it reports observed activity only. It does not detail update cadence or error behavior, but the annotations already cover safety and idempotency.

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 return values, then adds audience, the observed-only scope, the alternative tool, and cost. Every sentence contributes useful selection or invocation context without unnecessary repetition.

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 one-optional-parameter, read-only data tool with no output schema, the description explains the return contents, time window, source, cost, and scope limitation. Nothing essential for correct selection or invocation 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?

Schema coverage is 100%, so the hours parameter is already well documented as an optional integer from 3-168 with a default of 24. The description reinforces the default 24-hour window and the 7-day maximum, but it does not add substantial meaning beyond the schema.

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 gives a specific verb and resource: it returns the current planetary Kp index, storm level, and recent 3-hourly history. It also explicitly contrasts this observed-activity tool with kp_forecast_3day, so an agent can distinguish it from the sibling forecast tool.

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 clearly states when to use this tool: for current observed geomagnetic activity and whether a storm is under way. It also names the alternative, kp_forecast_3day, for the coming days, giving an explicit when-not/alternative rule.

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