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

Annotations already declare readOnlyHint and openWorldHint, and the description adds real behavior the annotations do not cover: licensing/attribution obligations, that no points are spent, and the concrete failure mode (privacy_consent_required until the controller accepts the current privacy version) with a warning not to fabricate acceptance. The 'supply fields' phrasing is muddled given only lat/lon exist, but the error-state disclosure is genuinely valuable.

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?

Purpose is front-loaded in the opening sentence and each later sentence carries distinct information (licensing, cost, consent error). The licensing and wttr.in clauses are slightly tangential to invocation but do head off plausible agent mistakes and attribution errors, so they mostly earn their place.

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 tool with annotations covering the safety profile and open-world access, the essentials are present. Without an output schema, though, the description never says what the response contains (units, timezone, how many hours, response shape), which leaves a meaningful gap for an agent consuming the result.

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 0%, so the description must carry the load; it does clarify that a single coordinate (not a URL or place name) is the input, and the schema supplies numeric ranges for lat/lon. Beyond that it adds no meaning about the two parameters, so it only partly compensates for the missing schema descriptions.

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 first sentence names the resource (hourly forecast), the scope (one coordinate), and the upstream provider (MET Norway), which is enough for an agent to distinguish it from unrelated hub_* siblings such as hub_sunrise or hub_geocode. It is a noun phrase rather than a verb-led statement, but the meaning is unambiguous.

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 rules out two wrong invocations (wttr.in is not proxied, no URL accepted) and says the call is free of point cost, which is useful selection context. However, it never states positively when this tool should be preferred over any alternative, nor what forecast horizon to expect, so usage is only implied.

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