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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile and external-call nature. The description adds the returned field set, which is useful, but omits the forecast horizon cap (max 16 days) and units, which matter for a forecast tool.

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 front-loaded sentence with no filler; the field list is efficient. It is arguably too terse given the undocumented parameters, but every word earns its 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 3-parameter tool with 0% schema coverage and no output schema, the description should explain the `days` range and coordinate requirements. It covers the return shape adequately but leaves input behavior gaps an agent would need to infer from the schema.

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 compensate, but it never mentions the `days` parameter (default 3, max 16) or what latitude/longitude require. It adds only the return-field semantics, leaving all three input parameters undocumented in prose.

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 output: current conditions plus a daily forecast with named fields (max/min temperature, precipitation, weather code). An agent instantly knows what it returns, though it doesn't explicitly name the data source behavior (Open-Meteo) beyond the title.

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?

Usage is implied by the weather domain, and no sibling tool covers weather so there is no real alternative to route to. However, it gives no guidance on when to prefer this over geocode_search for resolving coordinates, nor any prerequisite about needing lat/lon first.

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