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

Annotations already cover read-only, destructive, open-world and idempotency; the description adds the data source (Hyperliquid public API), the return shape (coin-to-price map), and a cost model (per-call pricing, first 25 free, failed calls free, repeats charged). The cost and idempotency-per-call disclosure is valuable context beyond structured data. Loses a point only because the closing 'reads or computes only and changes nothing' largely restates readOnlyHint.

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 with the core capability and scoped example, then use cases, pricing, and safety in a clean progression. The final clause about charging repeats is slightly redundant with the earlier pricing sentence, costing a small amount of tightness.

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?

For a single optional parameter tool with annotations but no output schema, the description covers source, return format, default behavior, filtering, cost, and side-effect profile. Nothing an agent needs in order to call it 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% and the schema already documents the default ('every perpetual') and the comma-separated symbol format. The description's example (coins=BTC,ETH,SOL) and 'only the coins you name' phrasing mostly repeat the schema, so the baseline of 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?

States a specific verb and resource ('Current mid prices of every Hyperliquid perpetual'), quantifies scope (~200 coins), and specifies the return shape (coin-to-price map) plus the filterable variant. The name 'perpetual' plus 'Hyperliquid' distinguishes it from generic siblings like crypto_price or price_tokens without needing 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?

Explicitly names intended uses (quick snapshot of many coins, portfolio marks, price ticker) and an exclusion with a named alternative: 'for funding and open interest use hyperliquid_market.' That is a genuine when-to-use/when-not routing instruction.

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