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

With no annotations, the description carries the burden and does disclose a genuinely important behavior: with lat/lon 'the nearest IPMA forecast location is used', so the agent knows results may be snapped to a nearby station rather than the exact point. It also lists the returned fields. It does not cover failure behavior for unknown place names or non-Portuguese coordinates.

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 core purpose is front-loaded in the first clause, followed by a compact parameter block and a one-line return summary. No sentence is 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?

An output schema exists, so the return-value sentence is a bonus rather than a necessity, and the location-snapping behavior is well covered. The gap is the all-optional parameter set with no statement of the valid call combinations or error conditions.

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%, but the description compensates well: 'place' is defined as a district capital or island town with four concrete examples, and lat/lon is framed as an alternative input mode. It does not state that at least one of the three optional parameters must be supplied, which is a real ambiguity given all params are optional.

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 (5-day weather forecast) with explicit scope: Portugal, IPMA as the official source. The scope statement alone separates it from siblings like sea_forecast and weather_warnings, which cover different domains.

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 place-vs-lat/lon argument split implies the usage pattern, and 'use instead of place for anywhere else' gives a selection rule between the two modes. But there is no guidance on when to pick this over weather_warnings or sea_forecast, and no note on what to do when a location is outside IPMA coverage.

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