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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses the free-tier daily per-caller quota and, importantly, where payment credentials go (X-Payment / X-Payment-Tx / Bearer token in MCP request headers, not in parameters). That is genuine operational context an agent cannot get from structured fields. It does not say what happens when the quota is exhausted or how failures surface.

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 same content is delivered three times — an English prose line, a [zh] block, and an [en] block that largely restates the first line. The result is bloated and buries the one non-obvious detail (payment headers) at the very end.

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 3-parameter tool with no output schema and zero schema description coverage, the description lists the returned metrics but leaves the parameters undefined, so an agent cannot confidently supply 'top' or 'expiry'. The payment/quota note is useful, but the parameter gap is material.

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 0%, so the description must carry parameter meaning and it does not. It merely repeats the names 'currency / expiry / top' and notes they are optional — something the schema already conveys via no required fields. The meaning of 'top' (top N by what?) and the expected expiry format are never explained.

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 opening line states a concrete purpose — an implied-volatility term-structure snapshot — and enumerates the returned fields (ATM IV, 25d skew, expiry count, total OI, nearest max pain). It does not distinguish this from the sibling options-iv.vol_surface, which an agent could easily confuse it with given the near-identical naming, so it stops short of a 5.

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 explicit when-to-use or when-not-to-use guidance, and no alternative tool is named. The only routing signal is the '免费'/'free tier' label, which implies a paid counterpart exists but never says when to pick that instead.

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