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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, but the description goes well beyond them: limit-up and limit-down are derived from previous close and tick size because the data carries no flag, the universe excludes ETFs and warrants, OTC is out of scope, and the data is a previous-day snapshot rather than live. The only shortfall is that it doesn't state the response shape or pagination behavior.

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?

Purpose, routing guidance and caveats are front-loaded and each English sentence carries distinct information. The entire content is then repeated verbatim in Chinese, which roughly doubles length without adding new facts for a single-language reader, though it may aid multilingual routing.

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?

An output schema exists, yet the description still sketches the row fields (code, name, close, change, percentage change, volume). Combined with the stated coverage universe, the derived-limit methodology, the source (TWSE OpenAPI) and the non-live timing, an agent has everything needed to select and call it correctly.

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's own text for `limit` is richer than the description, including the important note that limit-up/limit-down counts are unaffected by the limit. The description adds nothing about the parameter, so the 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 first sentence states a precise verb+resource+scope: percentage-change rankings among TWSE-listed stocks for the previous trading day, plus limit-up/limit-down counts. It explicitly names the sibling it is not (dataset.get sorted by price change, which ranks by absolute points). An agent can distinguish it from snapshot.market, snapshot.stock and dataset.get without opening any schema.

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?

It names the exact user intents that select this tool ("top gainers / top losers / which stocks hit the daily limit") and gives an explicit when-not with the alternative (don't use dataset.get's change sort; use quote.realtime for live prices). Both the exclusion and the correct substitute are stated, not implied.

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