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

With no annotations, the description compensates by disclosing the PRO plan requirement and 403 behavior for lower tiers, plus the date parameter exclusivity. It could further clarify default behavior when no params are provided, but the disclosed constraints add real value beyond the schema.

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 organized into title, requirement, args, and returns sections with no filler. It is efficient, though the title 'ETF 份额与规模（ETF）' is slightly redundant with the name and repeats ETF twice.

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 5-param query tool with an output schema, the description covers all parameters, the auth constraint, date exclusivity, and return fields. It remains vague on what happens when no parameters are supplied, but overall it's sufficiently complete for selection and invocation.

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% and the description's Args section directly mirrors the schema descriptions, adding no new semantic meaning for parameters. The Returns section lists output fields but doesn't enrich parameter understanding, so 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 description states the tool returns ETF share and size data (ETF 份额与规模), which clearly identifies the resource. It lacks an explicit verb like 'query' or 'get', and doesn't name sibling alternatives, but the fields and ETF scope distinguish it from sibling tools like etf_daily or nav.

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 specifies a hard requirement (PRO or higher, otherwise 403) and explains the trade_date vs start_date/end_date mutual exclusion. It does not explicitly list alternatives or when-not-to-use, but provides clear contextual usage for selecting date parameters.

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