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

Annotations already declare it as read-only, non-destructive, open-world, and non-idempotent. The description adds useful non-schema context: live public API reads, response shape, pricing/per-call billing, free first 25 calls, failed calls free, and that repeats are not free.

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 purpose and return shape are front-loaded and the alternative tool is named early. The pricing and billing details are relevant but slightly repetitive, especially the separate note that each call is charged and repeats are not free.

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 helpfully explains the return shape as a coin-to-price map. It covers usage, filtering, and billing, though it does not mention behavior for unknown or invalid coin symbols.

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 single coins parameter is already documented as optional comma-separated symbols defaulting to every perpetual. The description adds an example (coins=BTC,ETH,SOL), which is marginally useful but not necessary beyond the schema.

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 verb and resource: current mid prices of every Hyperliquid perpetual, returned as a coin-to-price map or filtered by named coins. It clearly distinguishes itself from the funding/open-interest sibling hyperliquid_market.

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 explicit use cases (quick snapshot, portfolio marks, price ticker) and explicitly routes funding and open-interest queries to hyperliquid_market. This leaves little ambiguity about when to choose this tool.

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