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

Annotations only declare readOnlyHint and openWorldHint, so the description carries real extra weight: it discloses cost ($0.005 USDC), the payment source (the caller's own wallet via x402), the ~3 min refresh cadence, and a 'stale data never charged' guarantee. These are genuine behavioral facts beyond the annotations, though response shape and behavior when coin is omitted remain unstated.

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?

Three tight sentences, front-loaded with what the tool returns, followed by freshness, price, and a short disclaimer. Nothing is redundant; the 'Not financial advice' line is boilerplate but defensible for a paid market-data tool.

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 zero-required-param, no-output-schema tool, the description covers the essential decision inputs: cost, data provenance, freshness, and payment authorization. The only gap is the semantics of the optional coin filter (all coins vs. one), which neither the description nor schema resolves.

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 100%, so both parameters are already documented, including the x402 payment_signature mechanics. The description adds nothing about coin (e.g., what is returned if it is omitted) and only echoes 'per coin', 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 and scope: net long/short positioning of large tracked Hyperliquid accounts, per coin, returning notional and counts. It is clearly distinguishable from siblings like hyperliquid_whale_liquidation_levels or hyperliquid_funding_extremes, though it never names an alternative explicitly.

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 context is implied rather than stated: the agent learns the price, the data source, and the staleness policy, which helps decide whether it is worth paying for. However, there is no explicit when-to-use/when-not guidance relative to the other Hyperliquid tools, and the 402/payment flow is only explained in the schema.

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