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

No annotations are provided, so the description carries the full behavioral burden, and it does disclose two consequential traits: the $0.03 USDC cost with atomic units, and that no API keys are required. It omits rate limits, pagination, or whether depth is aggregated, which keeps it short of a 5.

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?

Three sentences, zero waste, and the most decision-critical fact (paid, with exact price) is front-loaded before purpose and return shape. Every clause carries distinct information.

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 an output schema present and 100% schema coverage, the description needn't describe return values, yet it usefully previews the payload fields anyway. It covers cost, auth, and scope, so nothing essential is missing for a low-complexity public market-data call, though sibling disambiguation is absent.

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 description coverage is 100% and both parameters (coin with XBT→BTC/WETH→ETH normalization, nLevels max 100) are fully documented in the schema. The description adds no additional parameter meaning, so the baseline 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+resource+scope: 'Hyperliquid public L2 order book depth', and the hl_ prefix plus the exchange qualifier distinguish it from the generic book_depth sibling. An agent can tell at a glance what data comes back (bids/asks with price, volume, n, mid, imbalance).

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?

The description states a useful precondition ('Public API only — no keys') and flags that the call is paid, which implicitly gates usage. However, it never says when to prefer hl_book_depth over the sibling book_depth or basis_snapshot, leaving the selection decision to inference from the name prefix.

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