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

Annotations already declare read-only, idempotent, open-world, non-destructive, but the description adds substantive behavior: data source and provenance, a stale flag when the reading is over 30 minutes old, disclosure that the NOAA summary feed can lag by hours, and a 1-credit cost. That is real operational context an agent could not infer from the 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?

Front-loaded with the question it answers, then return shape, use case, staleness caveat, exclusion, and cost. Every sentence carries information, though the aurora-chaser sentence is slightly narrative and could be tightened.

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?

No output schema exists, so the description must describe the return value, and it does: speed in km/s, a plain-language level, the age of the reading, and a stale flag. Source, caveats, and cost are all covered, leaving nothing an agent needs 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 no parameters, so the baseline is 4 and there is no parameter meaning to add. The description correctly implies a parameterless 'current reading' call.

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?

States a specific resource and measurement: latest solar wind speed in km/s measured upstream of Earth, sourced from NOAA SWPC, plus a derived plain-language level. That is clearly distinct from siblings like kp_index_now, solar_flux_10cm, and aurora_chance_at_location.

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?

Gives a concrete use case (aurora chasers judging whether a CME or high-speed stream has arrived) and an explicit exclusion: it does not include Bz, which also matters for aurora. It stops short of naming the sibling that does supply Bz, so routing is implied rather than spelled out.

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