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

Annotations already declare readOnly, idempotent, open-world, non-destructive. Beyond those, the description adds genuinely useful traits: source is TWSE OpenAPI updated after each trading day (not live), three datasets are merged with parallel queries, and a section that cannot be fetched returns null plus a caveat rather than failing the whole call.

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-loads the core content (what the snapshot contains) before source, freshness, and failure semantics. The bilingual duplication roughly doubles length without adding new facts, but the structure stays purposeful and scannable.

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, return-value detail is not required, and annotations carry the safety profile. The description nonetheless covers freshness, source, and partial-failure behavior, leaving little an agent needs to know in order to call this correctly.

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 both parameters (code, include_realtime) are already documented in the schema. The description notes that include_realtime costs an extra outbound call, but that detail is also in the schema's own description, so it adds little beyond the baseline.

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 resource and scope: one TWSE-listed ETF with fund profile, prior-day price/volume, and regular-savings popularity. It is clear what the tool gathers, though differentiation from sibling snapshot.stock/snapshot.futures is only implicit via the 'ETF' framing, and explicit only for quote.realtime.

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: this is a non-live, after-close snapshot, and for current prices it points to quote.realtime. It provides a positive routing rule but states no explicit when-not or exclusion conditions for this tool itself, keeping it just below full marks.

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