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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds beyond annotations by explaining that the tool resolves a Swiss municipality to the nearest MeteoSwiss station and that it returns measurements only, not forecasts. This gives useful behavioral context without contradicting the annotations.

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 description is a single sentence that is front-loaded with the key information ('Latest measured weather') and includes the essential variables and the 'no forecasts' exclusion. Every word adds value; there is no repetition or 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?

The description, combined with full schema coverage, annotations, and an output schema, provides enough information for an agent to call the tool correctly. It could be slightly more explicit about behavior when 'place' is null or when the requested place is outside Switzerland, but these are minor gaps given the schema's default and 'Swiss municipality' qualifier.

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%, and the schema already documents both parameters well: 'place' explains accepted formats and language variants, and 'language' explains it is the user's question language. The tool description adds no additional parameter meaning, so the baseline score of 3 is appropriate.

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?

The description states a specific verb and resource: it returns the latest measured weather (temperature, humidity, precipitation, wind) from the MeteoSwiss station nearest to a Swiss municipality. It also clearly distinguishes itself from forecasts, so an agent can immediately understand what this tool does.

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 description gives clear context: use it for measured weather at a Swiss location, not for forecasts. It provides the when-not-to-use signal 'no forecasts,' but does not name any alternative tool for forecasts. There are no weather-related siblings to contrast with, making the lack of explicit alternatives less impactful.

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