option_chain

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

With no annotations, the description carries full responsibility for behavioral disclosure. It explains the dual behavior (expiries vs. strikes) and the date format, but it does not disclose details like how many strikes are returned, what 'near-the-money' means, or any rate limits. The core behavior is clear, but richer context is missing.

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?

The description is a single concise sentence that front-loads the action ('List') and packs all key information (underlying, expiry, format) without unnecessary words. 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 the tool's simplicity (2 params, output schema present), the description provides the essential mode distinction and parameter format. It does not explain the output structure, but the output schema presumably covers that. It could have mentioned how to choose between this and sibling 'option_contract', but overall it is adequately complete.

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 0%, so the description must add parameter meaning. It clarifies that the optional 'expiry' parameter toggles the output mode and specifies the required format (YYYY-MM-DD). It also implicitly explains that 'underlying' is the ticker or symbol. This compensates well for the lack of schema descriptions.

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 uses the specific verb 'List' and clearly identifies the resource: option expiries for an underlying, or near-the-money strikes for a specified expiry. It distinguishes itself from siblings like 'option_contract' by focusing on the chain/expiries rather than a single contract.

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 clearly implies use cases: provide just the underlying to get expiries, or add an expiry to get near-the-money strikes. It does not explicitly mention when not to use the tool or name alternatives, but the two-mode behavior gives clear context for when to call it.

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