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

Annotations only declare readOnlyHint, and the description adds substantial behavioral context beyond that: pending/missing outcomes are returned as null, original option timestamps are unavailable, and the endpoint currently returns 503 historical_source_unhealthy (daily_series_disabled) until the daily-series release is enabled. The 503 disclosure in particular prevents a wasted or misdiagnosed call.

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?

Three sentences carry real information (data content, null behavior, 503 gate), but the leading 'Alpha:' fragment is wasted and the first sentence is a dense jargon pile-up that delays the actionable facts. The critical 503 warning is buried at the end rather than front-loaded.

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 must convey return semantics, and it only loosely does so (sigma bands, terminal moves, breaches, nulls) without describing response shape, date alignment, or the holiday-adjusted tenor note already in the schema. For a historical-series tool with 5 parameters, more return-format detail would be expected.

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 symbol, start, end, tenor_days and apiKey semantics. The description adds no parameter-level detail beyond echoing the SPY/QQQ universe, 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 the specific data returned — reconstructed SPY/QQQ ATM-IV sigma bands versus matured terminal moves and intraperiod breaches — which lets an agent tell this apart from the contemporaneous get_expected_move. However it is phrased as an opaque data gloss ('Alpha: reconstructed...') with no clear verb like 'Returns', so the purpose must be inferred from the title.

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 explicit when-to-use guidance and no reference to alternatives such as get_expected_move or get_historical_volatility. The caveats given (null pending outcomes, fractions are not win probabilities) describe data interpretation, not when an agent should select this tool.

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