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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so safety is covered. The description adds genuinely new behavioral context the annotations cannot convey: the temporal scope ("today's conditions and the coming days, not a forecast for a later month") and the warning that warmest ranking puts deserts first.

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?

Front-loaded with the core action, then progressively narrower guidance. Somewhat dense with parenthetical examples and guillemets, but every clause carries routing information rather than filler.

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 an output schema present, return values need no explanation, and the description covers scope, ranking mode, region handling, and the key temporal pitfall. The only omission is any mention of locale/units behavior, which is left to the schema description.

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 100%, so baseline is 3, but the description goes beyond the schema by explaining intent mapping ("warm and pleasant" → default score; region=europe example) and the consequence of sort=warmest. It does not add format details for limit/locale beyond the schema.

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?

Starts with a concrete verb+resource: "List the N countries where today's weather is best for travelling by campervan, highest 0-100 travel score first." It also implicitly separates itself from the per-place siblings (get_country_travel_weather, get_city_travel_weather) by being the global ranking tool.

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?

Explicit when-to-use conditions: "when no country is named and someone asks where to go for warm or good weather right now," plus the region variant and a precise exclusion rule for sort=warmest that disambiguates "warm and pleasant." It also states the negative case (later-month forecasts are out of scope).

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