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

Beyond the safety annotations (readOnly, idempotent, non-destructive), it discloses non-obvious behavior: ~15 min data delay, that 'side' is an NBBO-location proxy rather than true buy/sell, and precise flag thresholds (away_from_quote = >0.1% and 2 cents). These caveats materially change how an agent should interpret results.

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 core purpose and the usage example placed near the end. It is dense and jargon-heavy (outside_nbbo, away_from_quote, cells_side), but nearly every clause carries substantive information rather than filler.

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 carries the full burden of describing return values and does so thoroughly: the grid shape, point of control and value area, block prints with report time, cell-level [buy, sell, away] shares, and added totals. An agent has enough to call and interpret it.

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 (ticker, date) are already documented in the schema. The description restates 'for a date (default latest)' but adds no syntax or format meaning beyond what the schema provides, so the 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 names a specific verb+resource (when one ticker's off-exchange/dark pool volume traded, by price, for a date) and enumerates the output (5-minute × price grid, point of control, value area, largest block prints). This clearly separates it from ranking/aggregate siblings like darkpool_ranking or short_volume, which don't describe intraday price-time structure.

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 supplies a concrete usage example ('Use for "when did the dark pool trade NVDA around 180?"') and states the date default (latest). It stops short of explicitly naming alternatives or when-not-to-use cases versus other dark pool/volume siblings.

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