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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds genuinely non-obvious behavioral context: the 403 error semantics ('PRO_SUBSCRIPTION_REQUIRED or DATE_RANGE_RESTRICTED error means the key's plan does not cover the request -- it does not mean the data is missing'), which prevents an agent from misinterpreting an auth failure as a data gap. It also discloses the row structure (one row per day, band plus instrument). This is more than the annotation layer alone provides.

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 compact sentences, each earning its place: the data definition, the use cases, and the error-handling caveat. The essential definition is front-loaded in the first sentence, and the operational note about API keys/403s is a valuable addition rather than filler. No redundancy with the schema or annotations.

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 correctly carries the burden of conveying return shape, and it does: lower_strike, upper_strike, the instrument, and one row per day. Combined with 100% schema parameter coverage, safety annotations, and the 403 diagnostic note, an agent has nearly everything needed to select and invoke the tool correctly. The only minor gap is that the date column is implied ('one row per day') rather than explicitly listed as part of the response.

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 all six parameters already documented in the schema (date formats, inclusive/exclusive semantics, max_rows cap). The description's mention of date-range backtesting aligns with the parameters but adds no syntax or meaning beyond what the schema provides. Per the rubric, baseline 3 is appropriate when the schema carries the documentation burden.

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 states precisely what the tool returns: 'a model-derived intraday range (lower_strike, upper_strike) that same-day S&P 500 index options are expected to stay within, plus the instrument it applies to. One row per day.' This is a specific data product with a concrete resource, scope, and row semantics that clearly distinguishes it from sibling data tools like get_iv_rank or get_momentum_index without needing to open the schema.

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?

The description gives clear, concrete use cases: 'structure 0-DTE trades -- e.g. sell iron condors with short strikes at or beyond the band, or fade band breaches -- and to backtest how often the band held over a date range.' This tells an agent when the tool is relevant. It does not explicitly name alternative tools or state when-not-to-use conditions, so it falls just short of a 5.

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