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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true; the description adds genuinely new context the annotations cannot convey: per-call USDC billing drawn from the key's SingIt limits, and Base-only account eligibility. It does not cover failure behavior (e.g. unknown ticker) or why idempotentHint is false for a market-data read, which keeps it short of 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?

Three tight sentences: what it returns first, then sibling routing, then billing/eligibility caveats. Every clause carries information an agent needs and none is redundant.

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 compensates by listing the returned fields, and it covers cost and account eligibility. Minor gaps remain (unknown-asset behavior, whether values are live or snapshot), but for a one-parameter read tool it is nearly complete.

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?

The single parameter has 100% schema description coverage with its own examples (BTC, ETH, SOL), so the schema already does the work. The description's 'e.g. BTC' restates that without adding format, casing, or error semantics, so 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?

Names a specific resource (a single Hyperliquid perpetual market) and enumerates what it returns: price, funding, open interest, max leverage, and size rules. It explicitly distinguishes itself from get_funding_rates, so an agent can route correctly without opening the schema.

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?

States the use case ('Hyperliquid's own contract details') and names the alternative plus the condition that selects it ('use get_funding_rates to compare venues'). It also flags the eligibility constraint ('Base accounts only for now'), leaving nothing to inference.

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