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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond annotations by specifying the returned fields, underlying instrument types, and available filtering dimensions, including a concrete invocation example.

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: one sentence for the core behavior, one for filters, and one example with realistic parameters. Every sentence contributes useful information with no repetition or filler, despite having to cover a fairly complex tool.

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 9-parameter tool with no output schema, the description covers the return-value highlights and all major filter dimensions, while the schema handles parameter details. It does not describe exact response formatting or potential response-size concerns, but it is sufficient for an agent to select and invoke the tool correctly.

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?

Input schema coverage is 100%, so the schema documents all nine parameters. The description summarizes filter categories (expiration, days-to-expiration, delta, side, liquidity) and provides an example, but it does not add meaningful detail beyond the schema's own parameter 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 a specific verb and resource: 'Get the full option chain for an underlying stock/ETF/index,' followed by the exact data fields returned (strike, bid/ask/mid/last, volume, open interest, IV, greeks). This clearly distinguishes it from siblings like marketdata_option_quote, marketdata_stock_quote, and marketdata_candles.

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 implies the tool is for retrieving full option chains and specifies available filters, but it does not explicitly state when to use this tool versus alternatives such as marketdata_option_quote for individual quotes. There is no direct when-to-use or when-not-to-use guidance.

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