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

With no annotations, the description carries the full load and does disclose key traits: data is after-hours and not real-time, each market carries its own data date, and the call takes no parameters. It does not mention response shape, latency, or any rate/source limits, which keeps it from a 5 in a zero-annotation context.

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 content is front-loaded with what is returned and closed with the critical timing caveat. The bilingual format duplicates content across Chinese and English, which aids clarity for mixed audiences but is mildly redundant rather than wasteful.

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 zero-parameter tool with no output schema and no annotations, the description supplies what matters: the data fields returned, per-market dating, and the non-realtime nature. Only minor gaps remain, such as units for the index and trading amount, which a caller may need.

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?

There are zero parameters and the schema is empty at 100% coverage, so the baseline of 4 applies. The description reinforces this by explicitly stating no parameters are needed, leaving no ambiguity about invocation.

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 resources returned (TWSE weighted index, TPEx index, trading amount, margin/short balances in lots) and gives the verb 'query', so the tool's purpose is unambiguous. It does not explicitly contrast itself with the sibling stock_quote, which an agent might otherwise confuse with an index-level summary, so a 5 is not warranted.

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?

'盤後資料，非即時' and '無需參數' tell the agent exactly when this data is appropriate (post-close lookups, not live trading) and that no setup is required. There is no explicit exclusion such as 'for individual stock prices use stock_quote instead', but the context is clear enough to guide selection.

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