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

Goes well beyond the annotations: discloses the data source (Hyperliquid public API), the cost model ($0.01/call via x402 USDC or card key /credits, first 25 free, failed calls free), and the fact that repeats are charged — consistent with idempotentHint=false. It also confirms read-only semantics ("reads or computes only and changes nothing"), reinforcing readOnlyHint=true with concrete detail.

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?

Return payload is front-loaded in the first sentence, followed by scope, usage, and cost — a sensible ordering. It runs slightly long, with pricing/auth detail consuming a full clause that could be tightened, but each sentence carries information an agent needs.

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 two-param, no-output-schema read tool, the description covers what is returned, the level range, the data source, cost/auth, and safety, leaving nothing material an agent would need before calling. Cost-per-call is especially valuable given the charged, non-idempotent nature of the endpoint.

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 both parameters are already documented. The description adds only the default and cap for levels ("Up to 20 levels a side (default 10)") and repeats the coin default, which restates rather than extends the schema. Baseline 3 is appropriate.

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+resource ("Live order book of a Hyperliquid perpetual") and enumerates exactly what is returned: best bid/ask, sizes, order counts, mid, spread in USD and bps, and summed depth. This is clearly distinct from hyperliquid_candles, hyperliquid_prices, and token-pricing siblings, though it never explicitly names a sibling or draws the line versus 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?

Gives concrete use cases: "judge liquidity and slippage before a trade, or for market-making and arbitrage checks," plus an invocation example (coin=BTC). It provides clear affirmative context but no exclusions or explicit alternatives for adjacent needs (e.g., when to prefer hyperliquid_market or hyperliquid_candles).

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