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

Beyond the readOnly/openWorld annotations, the description discloses caching (30 seconds), the exact cost ($0.002 USDC per successful call), the payment mechanism (x402 on Base, Solana or Arc), and that failed calls are not charged. These are material operational facts an agent needs before invoking a paid endpoint and are not present in the structured fields.

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?

It is front-loaded with the returned data and scoping rule, then the operational notes. The 'Information only, not financial advice' clause is boilerplate that a stricter reader might cut, but overall the sentences carry distinct facts with little redundancy.

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-field explanation is not strictly required, yet the description still covers scope, caching, cost and payment rails. It omits details like how 'limit' interacts with sorting or rate-limit consequences of the cache, but nothing critical to a correct call 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?

Schema coverage is 100%, so the schema already documents both parameters and the baseline is 3. The description adds genuine semantic value by clarifying that supplying 'coin' switches the call to a single-market lookup rather than a volume-sorted list, which is behavioral meaning the schema text does not convey.

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 names the specific resource (Hyperliquid perpetual futures) and enumerates the exact fields returned (mark/oracle price, funding, open interest, volume, max leverage), so an agent knows precisely what it gets. It does not, however, distinguish itself from close siblings like crypto_funding or perps_account, so it falls 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?

Usage is only implied via 'With coin, that market only' and 'sorted by volume' — enough to infer you can broaden or narrow scope, but there is no explicit when-to-use-this-vs-alternative guidance. With sibling tools covering funding and perps accounts, the routing rules are left to the agent.

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