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

Annotations already flag readOnlyHint=true and openWorldHint=true, so the bar is lower, yet the description adds real operational context: it is pay-per-call via x402 USDC on Base, and the response carries the payment challenge when payment is missing. That payment/auth behavior is exactly the kind of trait annotations do not convey.

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 compact clauses, front-loaded with the data delivered and followed by the payment model. No filler or redundancy.

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?

With an output schema present, return values need no explanation, and the description covers both content and payment behavior for a one-parameter tool. Only the currency parameter's role is left entirely to the schema, which is a minor gap.

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 100% for the single currency parameter, so the schema already documents the BTC/ETH default. The description adds no additional meaning about the parameter, which matches the 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 names a specific verb/resource: a Deribit volatility surface returning IV per expiry plus ATM greeks. That is concrete enough to separate it from siblings like funding, open_interest or btc_stats, though it never explicitly says so.

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?

There is no statement of when to use this tool versus alternatives such as funding or open_interest, and no conditions or prerequisites are given. The payment note describes mechanics, not usage guidance.

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