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

Annotations only declare readOnlyHint, so the description carries most of the behavioral burden and does so well: it discloses the N-PORT source, latest-period basis, ~60-day lag, FREE status, value-ranked top_holdings, derived weight caveat, and error semantics (opaque=true with reason vs DATA_UNAVAILABLE for outages). This is rich, actionable context beyond the annotation.

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?

Front-loaded with the primary action and highly information-dense, with almost every clause carrying necessary return, source, or limitation detail. The single long paragraph is a bit run-on and could be more scannable, but it is appropriately sized for a tool with no output schema.

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?

Because there is no output schema, the description must explain the return contract, and it does: it names the top-level and per-ETF fields, clarifies units, ranking, and non-summing weights, and covers the no-holdings and outage cases. For a read-only data-retrieval tool with minimal annotations, nothing essential appears missing.

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%, so the baseline would be 3, but the description adds meaning by saying top_holdings is value-ranked and confirming the default 10 / hard cap 50 behavior. It also clarifies tickers are ETF symbols capped at 25, beyond what the schema alone conveys about how the parameter is interpreted.

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?

States a specific verb, resource, and scope: 'expand up to 25 ETF tickers into the underlying holdings the fund ITSELF filed on Form N-PORT.' The Form N-PORT source distinguishes it from the sibling 13F holdings tools, so an agent can identify it without opening the 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?

Gives clear context and scope exclusions: 'HOLDINGS-ONLY: no yield, NAV or premium,' plus the 25-ticker limit and N-PORT filing basis. It does not explicitly name alternative tools for users who need fund fundamentals or NAV data, but the intended use is unambiguous.

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