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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds real value beyond them by disclosing the data source, license attribution, the fact that no paid/keyed access is involved ('Free'), and that the response spans current plus 3 days — but it says nothing about units, timezone, or request throttling.

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?

Two short sentences with the core scope front-loaded and no filler. The trailing fragment 'Free.' is slightly telegraphic but still informative rather than wasteful.

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 two-parameter read-only lookup with no output schema, the agent still lacks expected return values (units, temperature scale, number of forecast entries, timezone) and any operational constraints. The source/license disclosure is good, but the definition stops short of fully describing what the call yields.

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% and both parameters carry ranges, bounds, and worked examples, so the schema does the heavy lifting. The description only restates that lat/lon are the inputs and adds no format, precision, or unit guidance of its own; baseline 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 the resource (weather), the scope (current conditions plus a 3-day range), the required coordinates (lat/lon), and the upstream data source (MET Norway). No sibling tool is weather-related, so differentiation is trivially achieved, but it lacks an explicit verb and does not describe the shape of the returned forecast.

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 mention of prerequisites, and no statement of usage limits despite MET Norway's known rate/identification requirements. An agent infers only that it should supply coordinates for a location it cares about.

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