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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful context beyond annotations by naming the data source ('Yahoo Finance via yfinance') and stating 'No API key required,' which helps the agent understand access and operational expectations.

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 compact, front-loads the core purpose in the first sentence, and uses short bullets for usage conditions. Every sentence earns its place, and there is no redundant restating of the tool name or title.

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?

For a simple read-only expiry-date listing tool, the description covers the key context: what it does, when to use it, how it relates to GetOptionsChain, and the data source. An output schema exists, so the missing return-format details are not the description's burden; the only minor gap is that it doesn't warn that most parameters in the schema are irrelevant for this call.

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?

The schema_description_coverage is 0%, so the description must compensate for parameter semantics, but it only mentions 'a ticker' generically. It does not name the `symbol` parameter, clarify that most of the other schema fields are irrelevant to this tool, or explain expected formats. The schema itself contains some descriptions, but the description fails to bridge the low coverage.

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 opens with a specific verb and resource: 'List all available options expiry dates for a ticker.' It also distinguishes itself from the sibling tool GetOptionsChain by positioning itself as the step to run before requesting an options chain, so an agent can tell them apart immediately.

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 explicitly says 'Use this before calling GetOptionsChain' and provides a 'Use this tool when' section with concrete conditions: knowing which options contracts exist and needing an expiry date to pass into GetOptionsChain. This gives clear selection guidance without relying on inference.

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