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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely useful non-schema context: data is signed, it is not investment advice, and each call costs $0.01 USDC via x402 payable on Base or Solana — the payment requirement in particular is a meaningful behavioral disclosure.

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 usage trigger is front-loaded and the metric enumeration is dense but justified given there is no output schema. It is a long single stream rather than tightly grouped sentences, but no content is pure filler.

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 carries the return-value burden and does so thoroughly — price, multi-window moves, volume, open interest and its change, OI-cap proximity, funding detail, premium, max leverage and flags. Cost, payment chains and data signing are all disclosed, leaving nothing essential for a correct call.

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?

With a single parameter at 100% schema description coverage, the schema fully documents the coin format and case-sensitivity. The description's coin examples duplicate the schema examples and add no new parameter meaning, so this is the baseline 3.

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 states a specific resource and scope: stock/index/commodity/FX perpetuals on Hyperliquid (builder-deployed, HIP-3), with concrete coin examples like xyz:NVDA and xyz:GOLD. It implicitly separates itself from crypto-perp siblings (perp_full, crowd_perp) via asset class, but never names an alternative, so sibling disambiguation relies on inference.

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?

"Use before trading a ... perpetual" gives a clear, actionable trigger for when to call. There is no explicit when-not guidance and no named alternative for the overlapping perp tools, so it stops short of full routing clarity.

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