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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), and the description adds genuinely useful context beyond them: a per-call price of USD 0.003, the x402/USDC-on-Base payment mechanism, and the failure-billing policy. It does not mention rate limits or response shape beyond the field list, which keeps it below a 5.

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 sentences, front-loaded with what data comes back, then the cost model. Every clause carries distinct information with no repetition of the name or title.

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 no output schema, the description does the job of summarizing return content via its field list, and it discloses the paid-call model an agent must know before invoking. It could be more complete by noting response shape per token (object vs array) or whether omitted data is null, but the essentials are present for a one-optional-param read tool.

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% and the single optional 'tokens' parameter already documents its comma-separated format, 50-item cap, and empty-means-top-50 default. The description adds nothing about the parameter, so the baseline 3 applies.

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 enumerates the exact derivative metrics returned (funding rate per 8h, futures premium, open interest with 1h/24h change, long/short ratio) and the per-coin scope, which clearly separates it from siblings like prices or sentiment. It lacks an explicit verb ('retrieves/returns'), but the resource is unambiguous.

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?

Usage is only implied by the metric list — an agent can infer this is the tool for derivatives positioning data. There is no explicit when-to-use statement, no mention of when a sibling (e.g. prices_free, liquidations) is preferable, and no note on why one would choose the paid variant over free ones.

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