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

With readOnlyHint and openWorldHint already covering the safety profile, the description adds real value: it declares the tool is 'Free' and enumerates the metric outputs (gap %, range since, hours to next US open) that the absent output schema would otherwise leave unknown. It remains silent on data source latency and refresh cadence.

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?

A single sentence with no filler, front-loaded with 'Free.' and terminating in a compact colon list of outputs. The elliptical phrasing makes it slightly harder to parse than a plain sentence, but nothing is wasted.

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-parameter read-only metric tool with no output schema, the description supplies the return fields, the comparison basis, and the cost signal. Everything an agent needs to call it and interpret the result is present.

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 the property documents the market format with concrete examples (xyz:TSLA, xyz:GOLD, xyz:CL), so the schema does the heavy lifting. The description only broadens the category to 'stock, index or commodity' without adding syntax or constraints, matching the baseline 3.

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 the specific computation (a tokenized stock/index/commodity vs its Hyperliquid price at last Friday's US close) and what it yields (gap %, range since, hours to next open). It is distinctive against the sibling list, though the telegraphic phrasing requires a moment to parse. No explicit sibling differentiation, but the resource is unambiguous.

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 mention of 'weekend gap' and 'hours to the next US open' implies the pre-open/weekend context in which this is relevant, and 'Free' signals cost. But nothing states when to reach for this versus event_calendar, trade_conditions, or risk_check, and there are no exclusions or prerequisites.

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