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

Even though annotations already mark the tool as read-only and idempotent, the description adds valuable behavioral context about data freshness and the risk of presenting stale holdings as current. The warning about issuer files versus old filings is exactly the kind of non-obvious behavior an agent needs to know.

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 short, front-loaded with the core purpose, and every sentence earns its place. The imperative warning about lag_days is concise yet highly informative, with no wasted words.

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 output schema, the description partially fills the gap by naming holdings, weight, and age/lag_days. However, it omits top_n semantics and does not explain how the tool relates to sibling tools, so an agent still lacks some context needed to call and interpret it confidently.

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 0%, so the description carries the burden of explaining parameters, but it does not mention top_n at all and only implies ticker through context. The fields ticker and top_n are left to inference, making this a clear gap for a low-coverage 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 that the tool returns what a fund holds, along with weight and data age, which conveys the resource and output. The title 'Holdings of one ETF' reinforces the scope. It does not explicitly distinguish itself from sibling tools like etf_holders or etfiq_as_of, so it misses the top tier.

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 gives explicit operational guidance: always check lag_days before presenting the data, and explains why a current file and an old filing are not equivalent answers. It does not name when to prefer this tool over siblings or what to use instead, but the context is clear and actionable.

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