Daily forecast

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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so the safety profile is covered and the description is not required to restate it. The description does add value by naming the specific payload fields (temperature range, rain probability and amount, max wind). It says nothing, though, about how many days are returned or how the 'days' horizon affects the result.

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 dense sentence that front-loads the resource and then enumerates outputs in priority order. Every clause conveys information; nothing is padding.

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?

An output schema exists, so return values needn't be described, and annotations cover safety. The remaining gap is the forecast horizon: the description never mentions that a multi-day range (up to 16 days) can be requested, so an agent could reasonably read this as a single-day tool.

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%, including the 'Paris' / 'Paris, US' city format and the 1-16 day range, so the baseline of 3 applies. The description adds no parameter-level meaning beyond the schema and, in fact, its singular 'Daily forecast' framing is slightly out of step with the multi-day '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?

States a specific verb+resource ('Daily forecast for a city') and enumerates the returned measurements (min/max temperature, rain chance and amount, max wind), which makes it distinguishable from get_current by implication. It never names the siblings get_current or compare_cities, however, so the differentiation is inferential rather than explicit.

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 by the phrase 'Daily forecast for a city'; there is no statement of when to prefer this over get_current (current conditions) or compare_cities. No prerequisites, exclusions, or notes about forecast horizon are given, leaving the agent to infer routing from the tool name alone.

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