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

Annotations already declare readOnlyHint=true, so the read-only nature of this tool is covered. The description adds value beyond annotations by specifying the returned data fields (温度、天气现象、风力、湿度), which matters because there is no output schema. It does not mention rate limits or data freshness, so not a top score.

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?

Three sentences, each earning its place: capability plus return fields first, then usage triggers, then invocation guidance with a sample payload. Front-loaded and free of 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 tool is simple (2 params, one required, flat schema, no output schema), and the description covers what it does, when to call it, the shape of inputs, and what comes back. Nothing an agent needs to invoke it correctly is missing.

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%, so baseline would be 3. The description goes further by clarifying that the city should be given by name rather than latitude/longitude, and supplies a concrete example input {"city":"北京","days":3}, both of which reduce ambiguity when invoking the tool.

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 (查询) and resource (任意中文/英文城市的当前天气与未来数日预报), and enumerates the returned quantities (温度、天气现象、风力、湿度). No sibling tool overlaps with weather, so this is unambiguous against the full sibling list.

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?

Gives explicit trigger conditions in natural user-intent language ("某地天气/要不要带伞/未来几天温度"), which is exactly how an agent would recognize the need. Since no sibling competes with weather lookup, absence of an alternative tool reference is not a gap.

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