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

Annotations already cover readOnly, openWorld and destructive=false, and the description adds genuinely new context: newest-last ordering, "each call is charged, so repeats are not free" (which explains idempotentHint=false meaningfully), and a concrete price/free-tier model. Its "changes nothing" sentence largely restates readOnlyHint, which keeps it from 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?

Single dense paragraph that front-loads what the data is, then intervals/counts, then use cases, then cost. Almost every sentence earns its place, though the pricing/trial sentences are somewhat stacked and could be tightened.

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 only 3 optional parameters, rich annotations and no output schema, the description covers the bar contents and ordering effectively as an output summary, plus interval/count limits and cost. Nothing an agent needs in order to call this 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%, so the interval list, default of 50 bars and coin default are already documented. The description restates these without adding syntax, constraints or examples beyond "coin=BTC" (which is already implied by 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?

States a specific verb and resource ("Historical price candles (OHLCV)") and enumerates exactly what each bar contains, which cleanly separates it from sibling tools like hyperliquid_orderbook, hyperliquid_prices or hyperliquid_indicators. An agent can identify the output shape without opening the schema.

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 contexts ("charts, backtests, volatility and trend checks, or as context for a trading agent") and an example call, so the agent knows when this is the right tool. It stops short of naming alternatives or stating when NOT to use it, which would be the fifth point.

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