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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuine value by disclosing the unit convention and the USD conversion recipe (multiply by get_price), which prevents a common misinterpretation. It does not cover refresh cadence/staleness of the 'latest' reading or rate limits, so it stays above baseline but below rich behavioral disclosure.

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 short sentences, front-loaded with what the tool returns and its units, followed by the USD conversion recipe and sibling routing. No filler or restatement of the title.

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?

Output schema exists, so return values need not be enumerated, yet the description still flags the unit and the companion fields an agent must not miss. For a single-parameter read tool, nothing needed 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 market parameter already documents accepted forms (BTC-PERP, xyz:NVDA-PERP, HYPE/USDC, Hyperliquid names). The description only reinforces single-market scope via 'one Hyperliquid perp' and adds no syntax or format detail beyond the schema, so 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?

Names a specific verb and resource ('Latest open interest of one Hyperliquid perp') and pins down the otherwise ambiguous unit ('units of the base asset, BTC for BTC-PERP'), plus the extra fields returned (24h volume in USD, timestamp). The scope 'one perp' clearly separates it from aggregate/market-wide siblings.

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 routes the agent: cross-market comparison goes to get_markets_snapshot, historical series goes to run_query via describe_data, and USD conversion uses get_price. Both when-to-use and when-to-use-something-else are stated with the selecting condition.

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