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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely new context: the coverage area (contiguous US or Australia) is a hard constraint an agent could not infer from annotations, and the field list hints at the return shape. It says nothing about units, timezone, or data latency.

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 the resource first, the returned fields in a compact parenthetical, and the scope constraint last. No filler or redundancy.

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 right thing by listing the returned quantities, and it discloses the geographic restriction. However, for a tool whose schema is completely undescribed, it omits the forecast-horizon parameter and units, leaving real gaps an agent must guess at.

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 all three parameters (lat, lon, days) rest on bare titles. The description never mentions the 'days' horizon parameter at all, despite its 1–5 range and default of 3 being the main lever for the tool's behavior, and gives no format guidance for lat/lon.

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 (daily forecast summary) and enumerates the fields returned (min/max temperature, wind, gust, precipitation total), plus a geographic scope. The 'daily' qualifier implicitly distinguishes it from the current-conditions and generic forecast siblings, though it never names them.

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 only implied: 'daily' versus the sibling weather_current, and the stated limitation to the contiguous US or Australia tells an agent when this tool will fail. There is no explicit 'use this instead of X when...' routing and no mention of how the horizon (days) selects between this and a longer-range forecast.

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