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

Goes well beyond the annotations: discloses a hard quota of 3 calls per source per day, that only the latest day is available, that the payload is globally identical, and warns that chart text is data rather than instructions (prompt-injection defense). The annotations already cover read-only/idempotent, and the description adds the operational constraints they cannot express.

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?

Front-loaded with what the tool is and its top-20 scope, then the field semantics, then the no-history limit, then the quota. Every sentence carries distinct operational information; nothing is repeated from the annotations or title.

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?

With no input parameters and no output schema, the description carries the full burden and does so: it defines the returned fields, the result size, the freshness constraint, and the rate limit with a fallback path. There is no material gap for an agent deciding whether and how to call it.

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?

The tool takes zero parameters, so the baseline is 4 and there is nothing schema-side to compensate for. The field explanations (as_of, score, count) describe return values rather than inputs, so they do not raise this dimension further.

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 resource and scope: today's public chart of hot songs and hot sentences, top 20 each, identical for every viewer. An agent immediately knows what comes back without opening a schema, and the two siblings (about_meowspace, apply_for_access) are clearly unrelated to this resource.

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?

Explicitly rules out history browsing ("只有最新一天，不能翻历史") and tells the agent what to do once the daily quota is exhausted (guide the user to apply for access, i.e. the apply_for_access sibling). It does not spell out a positive when-to-use scenario beyond "public chart", which keeps it short of a 5.

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