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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), but the description goes well beyond them: sign convention ('Positive = longs pay shorts'), venue settlement intervals driving normalization, per-call pricing with a free tier, x402 payment-required behavior, and error semantics (isError on invalid input/upstream failure, not charged). This is unusually rich disclosure for a read-only tool.

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?

Purpose and sign convention are front-loaded, and each subsequent element (normalization, use case, alternative, price, errors) earns its place. It is dense and slightly packed into dash-separated clauses, but there is no filler or repetition.

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-value explanation is unnecessary, and the description still supplies the interpretive context an agent needs: the sign convention, cross-venue normalization, pricing/quota behavior, and error handling. Nothing material for correct invocation is missing.

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?

There is a single parameter with 100% schema description coverage ('BTC, ETH, SOL…'), so the schema already carries the semantics. The description adds no additional constraint beyond the implied coin scope, 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?

States a specific resource (perpetual funding) with explicit scope (one coin across Hyperliquid, OKX and Kraken Futures) and names what it returns (per-interval rate, annualized APR, open interest, mark price). It is clearly distinguishable from the sibling hyperliquid_markets, which it explicitly points to for market-wide scans.

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?

Gives explicit use cases ('basis/carry trades or crowding signals') and an explicit when-to-use plus an exclusion: 'For one coin across venues; to scan every Hyperliquid market use hyperliquid_markets.' The alternative tool and the condition that selects it are both named.

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