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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower; the description still adds two things beyond them: the output is grouped by expiry, and access is gated ('Pro'). The band semantics (fraction of spot) are also surfaced, though return payload details and rate limits remain unstated.

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 sentences, zero filler, with the scope constraint front-loaded ahead of the usage sentence. Every clause earns its place.

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 should ideally say more about the return shape; it gives the 'grouped by expiry' hint but not the fields. However, annotations fully carry the safety profile and the schema fully documents inputs, so the definition is adequate for correct invocation.

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 all three parameters are already documented, including the default width of 0.05 and the date format. The description only restates the default band as 'plus or minus 5%', adding a little interpretive value but nothing the schema lacks. Baseline 3 is appropriate.

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 verb+resource: returns near-the-money option strikes grouped by expiry, scoped to a band around spot. It distinguishes itself from a general chain by the ATM/band framing, but never names the closely related siblings contract_chain or contract_historic, so an agent must infer the boundary.

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?

'Use to find the liquid at-the-money contracts for a ticker' gives usage context, but there is no explicit when-to-use-vs-alternative guidance despite contract_chain and contract_historic sitting right beside it. The reader can infer the niche but gets no routing rule.

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