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

Annotations already declare read-only and closed-world, but the description adds meaningful context beyond them: data is a stored snapshot (not live), pagination is cursor-based, the response exposes provider count vs stored count vs covered weight, and isComplete=false/null means partial coverage. The only omission is any mention of freshness or staleness of the stored snapshot.

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?

Four short sentences, front-loaded with what the tool returns. The future-feature sentence about historical as-of selection earns its place by preempting a likely agent assumption, though it could be trimmed slightly.

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 an output schema present the description needn't enumerate return fields, yet it usefully summarizes the completeness signals an agent must interpret. Combined with 100% schema coverage and read-only annotations, an agent has enough to call it correctly; only explicit sibling routing for historical/exposure use cases is 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 description coverage is 100%, so ticker, limit, and cursor are fully documented in the schema itself. The description reinforces cursor pagination ('opaque cursor pagination') but adds no format or syntax detail beyond what the schema already provides, 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 gives a specific verb and resource — 'Return the latest stored ETF holdings snapshot' — and the word 'stored' plus 'snapshot' signals this is a persisted holding list rather than the exposure/aggregate views offered by siblings like get_etf_exposures or get_etf_snapshot. It stops short of explicitly contrasting itself with those siblings, so an agent must infer the distinction.

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?

'Treat isComplete=false or null as partial look-through data' and the note that historical as-of selection is not yet available give real usage context. However, there is no explicit statement of when to choose this over get_etf_exposures or get_etf_fund, which are the closest alternatives in the sibling list.

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