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

Annotations already cover read-only, idempotent, open-world, non-destructive behavior. The description adds non-obvious context the annotations don't: tier-gated result counts (free top 3, Pro up to 50) and that results span both expansions and compressions.

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?

Two compact sentences, metric definition front-loaded, with the usage cue and tier limits appended. No filler, though the tier sentence could be seen as secondary detail rather than essential.

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?

Low-complexity, zero-required-parameter list tool with no output schema and annotations covering the safety profile. The description supplies metric scope and tier limits; only richer direction semantics and return ordering are unstated.

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 50%; 'limit' is fully documented with default and bounds. The description's 'expansions and/or compressions' and 'up to 50' loosely map to the direction enum and limit ceiling but add little beyond the schema's own enum values.

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 metric and comparison basis: 30-day at-the-money implied volatility moved most versus prior close. An agent can distinguish it from oi_movers and volatility_term_structure by the IV-move focus, though no sibling is named explicitly.

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 a concrete usage trigger ('which stocks saw the biggest IV spikes today?') and states tier-based result caps. It lacks explicit when-not-to-use or named alternatives (e.g., oi_movers for open-interest movers), leaving some routing to inference.

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