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

The readOnlyHint annotation already tells the agent this is a safe read operation. The description adds detail about the data contents (e.g., 'per expiry', specific skew metrics) but does not disclose additional behavioral traits such as return format ordering, rate limits, or any special handling. This is adequate but not rich, so a 3 is appropriate.

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 consists of two concise sentences. The first lists the tool's output metrics, and the second provides usage guidance. Every clause earns its place with no redundancy or filler. It is front-loaded with the core noun phrase and immediately informative.

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 read-only tool with two parameters, the description covers the key aspects: what data is returned (skew metrics per expiry) and when to use it. The readOnlyHint covers safety. There is no output schema, but the description's enumeration of metrics compensates. Minor gaps like expiry ordering or return structure are not critical for a tool of this simplicity, so a 4 is warranted.

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%, with both `apiKey` and `symbol` clearly described in the schema. The description itself does not elaborate on parameters beyond implying that all expiries are returned, which is not tied to a parameter. Since the schema fully documents parameters, the description adds minimal extra value, earning a baseline 3.

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 clearly states the tool's purpose: 'Volatility skew term structure per expiry' and enumerates specific metrics (ATM IV, 25-delta and 10-delta risk reversal, butterfly spread, skew_25d, tail convexity). It distinguishes this tool from siblings like get_term_structure by focusing on skew-specific measures. The 'Use for' clause reinforces the exact intended application.

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 sentence 'Use for put/call skew across expirations, 25-delta risk reversal, butterfly convexity, or comparing near-term vs far-term skew' provides explicit guidance on when to use this tool. However, it does not name alternative tools or state when not to use it, so it falls short of a full 5.

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