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

With no annotations, the description carries the full burden and does well: it discloses the fixed start date (2026-04-13), the default window (20 days unless limit is given), the sort order (newest first), and the exact columns returned. It stops short of declaring read-only semantics or what happens when an asset has no records in range.

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 content is front-loaded and dense with no filler, packing the time window, record fields, ordering, and default limit into one compact statement. The telegraphic '20:00→08:00' notation and the phrase 'where the prices met' are slightly cryptic but not wasteful.

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?

There is no output schema, so the description must explain return values, and it does so by listing the recorded fields and their ordering. Combined with the disclosed time window and default limit, an agent has enough to call the tool, with only the limit unit and empty-result behavior left unresolved.

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?

The asset enum is fully documented in the schema, but limit has no schema description; the description supplies its default ('20 days unless limit is given') yet leaves the unit ambiguous — days of history versus number of rows. That partially compensates for the 50% coverage but doesn't fully resolve the parameter's meaning.

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 names the resource (past re-open records, per day) and enumerates the recorded fields: Hyperliquid move while closed, actual re-open move, follow flag, and meeting price. The historical framing ('Past ... record') implicitly separates it from the predictive sibling predict_open, though the contrast is never made explicit.

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?

Usage is only implied: 'Past' signals this is the retrospective counterpart to predict_open, but the description never states when to pick this over get_arbitrage or predict_open. There are no stated prerequisites or exclusions, leaving the agent to infer the historical-vs-predictive split from the wording alone.

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