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

readOnlyHint=true already establishes the safe-read profile, and the description adds genuine context beyond it: the model basis (ATM-IV 1-sigma) and an explicit caveat that the band is a model output, not an observed straddle price or execution breakeven. That interpretive warning is exactly the kind of value annotations cannot carry, though return format/pagination and any expiry-omission behavior are not described.

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 tight sentences: the first front-loads what is returned, the second front-loads the interpretive caveat. No filler, and the most decision-relevant content comes first.

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 read-only, 3-parameter query with full schema coverage and no output schema, the description usefully enumerates the return fields and warns against misreading the band as a tradable price. It is nearly complete, but omitting any pointer to get_expected_move_history leaves the agent without a routing signal among very similar tools.

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%, with apiKey, expiry, and symbol all documented in the schema itself (including 'omit for all expiries' and the OAuth/apiKey distinction). The description adds no parameter-level detail beyond restating 'per expiry', 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?

States a specific resource (expected move) and the exact method that produces it (ATM-IV-derived 1-sigma), per expiry, plus the concrete outputs (dollar/percent range, bounds, ATM IV). It clearly distinguishes itself from an observed straddle price or breakeven, but never names or contrasts with its obvious sibling get_expected_move_history, so sibling differentiation is incomplete.

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?

There is no guidance on when to reach for this tool versus get_expected_move_history, get_volatility, or get_levels, nor any stated prerequisites or input conditions. The 'not a straddle price / breakeven' line clarifies interpretation, not when-to-use, so an agent still has to infer the trigger.

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