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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds genuinely new behavioral context: a per-call price of $0.001/call and a precise picture of the payload, including that hours triggers an added funding_history block. That cost disclosure is exactly the kind of context annotations cannot carry.

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 dense and telegraphed, but every clause carries information: field names, nested shapes, the hours effect, cost, and the sibling redirect. Nothing is padded. The only cost is readability — the field list is packed into one run-on opening clause rather than front-loading the purpose first.

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?

There is no output schema, so the description must carry the full return shape, and it does down to nested funding fields and the conditional funding_history block. Cost, parameter effect, and the coin_snapshot alternative are all present. Nothing an agent needs to call this correctly 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 baseline would be 3. The description exceeds that by explaining the consequence of the hours parameter — 'hours=N (≤168) adds funding_history' with its stats and hourly array — which tells the agent what it gets for the extra parameter rather than just its range. Coin semantics are left to the schema examples.

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 a specific resource (one Hyperliquid main-dex perp) and enumerates exactly what comes back: mark_oracle_premium_bps, impact_premium_bps, funding, predicted_funding, open_interest_usd. The closing clause 'Use for one Hyperliquid perp's premium vs oracle...' states the purpose plainly. It only loses polish because the lead is a field dump rather than a verb-led statement of purpose.

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?

It gives a positive use case (premium vs oracle, predicted funding vs Binance/Bybit) and names the alternative explicitly: 'for the full coin picture use coin_snapshot.' That is real routing guidance. It does not cover other plausible alternatives among the many siblings (carry_spot_perp, br_premium, impact_for), so it falls short of a full when/when-not map.

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