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

Beyond readOnlyHint/openWorldHint, the description discloses metered pricing ($0.001 USDC per call via x402), that failed calls are free, the two-step quote/payment handshake, the sign convention for funding, and the not_found error shape. This is rich behavioral context the annotations do not provide and there is no contradiction with them.

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?

Front-loaded one-line summary followed by clearly labeled sections (When to use, Use instead, Parameters, Returns), which is easy to scan. It runs long and restates several schema-level parameter details, so it isn't maximally tight, but no sentence is wasted.

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 supplies a Returns breakdown covering every returned field, plus error handling and the payment lifecycle. For a 5-parameter, 0-required, open-world read tool, an agent has everything needed to invoke it correctly.

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 baseline is 3, but the description adds meaning beyond the schema: the funding sign convention, that sort/limit only apply when coins is omitted, and that funding_hours requires exactly one coin (and pulls history). Some parameter text is redundant with the schema, which keeps it from a 5.

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 verb and resource ('Hyperliquid perpetuals') and enumerates exactly what data is returned: mark/oracle price, funding, open interest, volume, leverage. It explicitly distinguishes itself from siblings crypto_market_pulse and token_price, so an agent can route without opening either 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?

Contains dedicated 'When to use' and 'Use instead' sections naming two concrete alternatives and the condition that selects each. It also clarifies the payment flow (call without payment to get a quote) and the coins-vs-top-markets branch, 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.