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

Annotations already declare readOnly, non-destructive, closed-world, so the safety profile is covered. The description adds real value beyond them: per-plan data freshness differences, the unusual behavior that a Free-plan call returns an upgrade note rather than an error, and the withholding rule for chain-wide figures. It still says nothing about pagination, response shape, or latency/rate limits, which keeps this at a solid 3 rather than higher.

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?

Front-loaded with the metric inventory, then short clauses for the withholding rule, interpretive caveats, plan tiers, and ticker scope. It is dense but nearly every clause carries information an agent needs. The interpretive disclaimer ('Nothing here is a forecast, and gamma carries no dealer sign') is arguably for the end consumer rather than the calling agent, a minor tax.

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?

No output schema exists, so the description must convey the return contents, and it does so thoroughly by naming each computed figure and stating which figures are omitted. Plan-tier behavior and the ticker universe constraint round out what an agent needs to call this correctly and interpret the result.

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 100% with only two parameters, both documented inline, so the schema already carries the load and baseline 3 applies. The description adds a marginal constraint ('US tickers only') and restates the nearest-expiration default, but gives no guidance on how expiration interacts with the metrics or what happens for an expired/invalid date.

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?

Opens with a specific verb and resource ('Get one expiration's positioning from the live chain') and then enumerates exactly what is returned: open interest and volume by side, put/call ratios, max pain, ATM IV, ATM straddle mid as expected move, 25-delta skew, top gamma strikes, and heaviest volume-to-OI contracts. That enumeration, plus the line about figures requiring the whole chain or one open-interest date being withheld, lets an agent distinguish this from GetOptionChain, GetPutCallRatios, and GetOptionTermStructure without opening another 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?

Clear context cues: defaults to the nearest upcoming expiration, US tickers only, and an explicit statement that Plus gets delayed indicative quotes while Pro gets real-time and Free is answered with an upgrade note. What is missing is an explicit routing statement naming the sibling for the full chain (GetOptionChain) or for a specific contract (GetOptionContract), so the agent must infer the boundary from the 'withheld' sentence.

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