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

Annotations already declare readOnly, idempotent, openWorld, non-destructive, so the safety profile is covered. The description adds substantive content context beyond that: the comparison against the stock's own 20-day average and the 'latest trading day' scope for the market-wide mode. It does not mention rate limits or pagination, keeping it just short of a 5.

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?

A single, front-loaded sentence that covers both modes economically, with the 'Data, not investment advice' disclaimer earning its place as a constraint. It is slightly dense but contains no filler or repetition.

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?

An output schema exists, so return-value structure need not be explained, and annotations cover the safety profile. The description fills the remaining gaps by specifying what metrics are computed in each mode and the 20-day baseline comparison. Only minor operational details (e.g., default window behavior) are left implicit.

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 the schema already documents days, limit, ticker, and minVolume (including that minVolume is market-wide only). The description's ticker-conditional behavior largely restates what the schema says ('optional; without it: market-wide leaders'), adding little semantic value beyond the schema 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?

The description states the specific resource (off-exchange/dark pool trading), the exact metrics returned (daily off-exchange volume and short volume, short share vs its own 20-day average), and the two operating modes (single ticker vs market-wide leaders). An agent can tell exactly what data this returns 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?

It clearly delineates the two usage modes: provide a ticker for per-stock daily series, or omit it to get the latest day's highest off-exchange short share and volume leaders. It does not name any alternative sibling tool or state when not to use it, but the mode split gives strong practical guidance.

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