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

With no annotations, the description carries the full disclosure burden. It explains the 20+ day history requirement, the two output modes, and the specific side=both behavior. It does not describe the response shape or behavior for insufficient history, but the core behavioral traits are well disclosed.

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 dense sentences, front-loaded with purpose, then organized by mode with a concrete example. Every clause earns its place; there is no filler or repetition of schema content.

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?

For a dual-mode tool with no output schema and no annotations, the description provides enough to select the right mode and parameters, and it surfaces the rolling-history prerequisite. Minor gaps remain, such as behavior when symbol is combined with snapshot-only parameters and what the returned records contain, but these do not block correct tool selection.

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 67%, and the description adds meaningful parameter logic beyond the schema: lookback_days and limit apply to the series mode, while side, min_rank, and max_rank apply to the snapshot. It also clarifies that side=both ranks by the higher of call/put IV rank, which the schema does not convey.

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 precise computation ('IV rank and IV percentile per symbol against its rolling history') and immediately separates the two modes: per-symbol time series versus ranked snapshot. This clearly distinguishes the tool from the sibling flow/OI tools and leaves no doubt about what it does.

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 gives an explicit mode-selection rule: pass a symbol for a time series, omit it for a ranked snapshot. The example 'side=put&min_rank=0.8 finds elevated put IV' provides concrete usage context. It does not name alternatives or state when not to use the tool, but no sibling tool overlaps with IV rank, so the guidance is clear.

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