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

With no annotations, the description carries the burden of explaining behavior. It discloses the return format (JSON array with specific fields), the mutual exclusivity of trade_date against start/end, and the exact-match behavior for symbol. It does not mention any side effects, permissions, or rate limits, but for a read-only data query, this is adequate. The description adds value by detailing the output fields.

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 description is concise and well-structured, with a clear title, an Args section, and a Returns section. Every line is informative and there is no redundancy or fluff. It fits the tool's simplicity.

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 description covers the essential aspects: what it does, the parameters, and the return structure. However, it lacks explicit guidance on when to use this tool vs similar daily-data tools, and it doesn't mention any pagination or limits. Given that an output schema is present (as indicated), the return field list is a helpful addition, but the absence of usage differentiation makes it slightly incomplete.

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?

All four parameters already have descriptions in the schema, and the description largely repeats those descriptions verbatim. It adds no new semantic meaning beyond the schema, such as examples or edge cases. The only additional context is the explicit note that trade_date is mutually exclusive with start/end, which is already present in the schema's trade_date description. Therefore, the description adds minimal value over the schema.

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 clearly states 'ETF 日线行情（ETF）' which identifies the tool as providing daily market data. It further specifies that the symbol can be ETF, sector, forex, HK stock, etc., giving a broad but clear scope. However, it does not explicitly distinguish itself from sibling tools like 'daily' or 'index_daily', so it's not fully differentiated.

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?

The description provides a usage pattern with parameters, implying it is used for retrieving daily market data for a given symbol over a date range or single date. It does not explicitly state when to prefer this tool over alternatives such as 'daily' or 'fx_daily', nor does it list any exclusions. Therefore, usage guidance is only implied.

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