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

Beyond readOnlyHint/openWorldHint, the description discloses the data source (Open-Meteo), that results are live rather than from training data, and that no API key is needed. These are genuinely useful behavioral facts an agent could not infer from annotations. It omits error handling for unknown cities and any rate-limit behavior, keeping it short of a 5.

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 English portion is front-loaded and efficient, but the entire text is duplicated in Chinese, roughly doubling length without adding information. The bilingual format may serve locale needs, but purely as agent-facing content half the description is redundant.

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 two-parameter read-only tool with no output schema, the description usefully lists the fields returned and the forecast horizon, which compensates for the missing output schema. The only notable gap is what happens with an unrecognized city name.

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 both city and days are already documented in the schema, and the description's mention of '1-7 day' merely restates the days constraint. It adds no syntax guidance such as how to disambiguate cities with the same name.

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 a specific resource (real-time weather and 1-7 day forecast) and scope (any city worldwide), and enumerates the returned metrics (temperature, feels-like, humidity, wind, precipitation probability). No sibling tool covers weather, so there is no ambiguity with exchange_rate, ip_lookup, or the mycel_* tools.

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 only implied by the word 'weather'; there is no explicit when-to-use or when-not-to-use statement and no named alternative. Given the sibling set, no real alternative exists, which limits the harm, but the guidance is still inferential rather than stated.

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