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

Annotations already provide readOnly/idempotent/non-destructive safety, so the description adds extra value by disclosing data provenance (MET Norway/yr.no), geocoding via OpenStreetMap, UTC/local time behavior with IANA tz, the 9-day limit, and per-call pricing. This goes well beyond structured annotations and helps the agent anticipate costs and output semantics.

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 compact and front-loaded: the core function and data elements appear first, followed by source, geocoding, time, and pricing in a few sentences. Every sentence carries information and no words are wasted.

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 read-only data lookup with no output schema, the description provides a rich picture: metrics, forecast length, place format, time handling, provider, and cost. Minor gaps remain — units (Celsius/Fahrenheit) and error behavior for unknown places — but these do not prevent correct invocation.

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 67% (place and tz are described, days is not). The description clarifies 'any place name or lat,lon' and explains how tz affects output, and implicitly adds meaning to days by tying it to the forecast length ('up to 9 days'). It effectively compensates for the undocumented days parameter.

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 states a specific function (current weather + hourly/daily forecast) for a resource (any place name or lat,lon) and enumerates the data fields. It clearly differentiates from siblings like geocode or sun_moon by specifying weather metrics and forecast range.

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?

The description implies the use case — obtain weather for a place — and adds useful context about data source and time handling. It does not explicitly name alternatives or exclusions, but no direct sibling weather tool exists, so the context is sufficient.

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