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

The annotations already establish this operation as read-only, open-world, and non-destructive, so the description does not need to restate safety. The description does add useful context beyond those annotations: the upstream data source, Open-Meteo, and its CC-BY 4.0 license, which implies an attribution obligation. It does not state units (metric vs imperial), the language of the output, or the freshness or caching of the weather data.

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?

This is one compact sentence that leads with the core capability and then gives provenance, with no filler. Every clause carries information the agent would otherwise be missing.

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?

For a simple read-only tool with an output schema that documents return values, the description covers scope, bilingual city support, and data provenance. The remaining gap is the zero-required-parameter behavior: the description never states what the tool returns if no city is supplied, and it does not state units.

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%, and the single city parameter is fully enumerated with slugs, so the schema already carries almost all of the documented meaning. The description reinforces the intent of that parameter by mentioning '16 cities (Chinese + English)', but it adds no format or resolution rules beyond what the schema documents, and it does not explain what happens when the parameter is omitted even though the parameter is not required. Baseline 3 applies.

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 names the specific resource and scope: 'Current weather + 7-day forecast for 16 cities', and adds that city names come in Chinese and English. An agent immediately knows this is a weather-reporting tool, though it does not explicitly differentiate itself from any sibling (none of the siblings are weather-related, so the need is lower).

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 implied by the phrase 'current weather + 7-day forecast' and by the fixed list of 16 cities, which tells the agent the tool is limited to those locations. However, there is no explicit statement about when to use this tool rather than other tools or other sources, and no guidance on how to handle requests outside the city list.

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