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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds real behavioral context by disclosing the upstream providers and the geographic routing/fallback logic (EC in Canada, NWS in the US, MET Norway as fallback), but it says nothing about error behavior, latency, caching, or freshness of the data.

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?

A single dense sentence that front-loads what the tool returns before listing providers. Every clause carries information, though the provider list is slightly long relative to its decision value for the agent.

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 output schema, the description does the work of conveying return content and units, and the input schema fully covers the three parameters. It is nearly complete; only the granularity of 'current conditions' and the exact forecast structure are left implicit.

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%: lat/lng units (WGS84, sign convention) and tz_offset_min's default are all documented in the schema. The description adds only output-unit semantics, not parameter meaning, so the baseline of 3 applies.

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 resource and scope: current conditions plus a 3-day outlook, with the exact returned variables (min/max °C, rain mm, wind km/h). It is clearly distinguishable from siblings like road_reports or wildfires, though it never explicitly contrasts itself with the closest sibling, report_conditions.

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?

There is no when-to-use or when-not-to-use guidance, no prerequisite or limitation stated, and no alternative tool named. The only usage signal is implicit: it takes a lat/lng point, so it is a point-forecast lookup, but that is left for the agent to infer.

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