The book for one date

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

Annotations already disclose read-only and open-world hints, so the description does not need to restate safety. It adds value by clarifying that the tool returns the real quoted book for a single expiry—including both contracts—rather than a theoretical or proposed structure, which is a meaningful behavioral distinction from sibling tools.

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 dense sentences with no filler: the first front-loads the payload scopeabb, and the second gives the selection cue. Every phrase 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?

Given a rich output schema, well-described parameters, and annotations covering the read-only behavior, nothing essential is missing. An agent can correctly select and invoke the tool from the description and schema alone.

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 67%: around and expiry_ts have descriptions, while currency is represented by an enum. The description adds no parameter-level detail, so it does not enrich the schema, but the schema already carries most of the parameter 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 names the resource (option chain), the scope (one expiry), and the returned fields (bid, ask, mark, implied volatility, delta for both call and put). It also distinguishes itself from proposal-making siblings by framing this as 'the actual book' rather than a proposal.

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?

It gives an explicit trigger condition: use when you need to reason about the actual book rather than take a proposal. This provides both a when-to-use signal and an implicit when-not-to-use contrast against the proposal-generating siblings.

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