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

With no annotations, the description carries the burden of behavioral disclosure. It adds important context: requires a ChainHelix API key as bearer token or a per-call fee paid via specific crypto networks, and it explains the comparison logic (latest hour vs 24 hours earlier within the same moneyness band definition). It does not discuss rate limits or side effects, but as a read-only data query, the disclosed access and measurement behavior is reasonably transparent.

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 not well-structured: the first sentence is a long, detailed billing specification that front-loads payment mechanics rather than the core purpose. The second sentence is dense but contains the actual function. A more concise arrangement would state the tool's purpose first and summarize access requirements.

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?

An output schema exists, so return values are covered. However, the description fails to mention what happens when the optional parameters are omitted, and it doesn't address defaults or potential errors. Given the tool's complexity and payment requirements, more contextual guidance would make it easier for an agent to invoke 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?

Since schema description coverage is 0%, the description must compensate. It maps 'Bitcoin and Ether' to the currency enum (BTC/ETH) and explicitly lists the horizon enum values (front, short, mid, long), adding meaning to both parameters. It doesn't clarify optionality or default behavior, preventing a 5.

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 identifies the tool as returning a Bitcoin and Ether options volatility surface from Deribit, with a detailed list of metrics (ATM, put/call IV, risk reversal, butterfly, open interest). It names the resource and parameters, but does not explicitly differentiate it from sibling tools like iv_summary or open_interest.

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?

No guidance is given on when to use this tool versus alternatives. The description focuses on payment/auth requirements and data details, but never mentions when this tool should be selected over iv_summary, open_interest, or other related volatility tools.

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