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

No annotation contradiction. Even with readOnlyHint true, the description adds useful behavioral context: real-time data, free access, optional filtering, and the specific fields provided. This goes beyond the annotations without overpromising.

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 description is front-loaded with the asset class and data fields, then covers the optional filter. It is slightly dense with parenthetical examples but remains efficient and relevant.

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 read-only price lookup tool, the description covers sources, return fields, and filtering. It does not document output format or edge cases, but that is not critical given the tool's simple, safe nature and the provided annotations.

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 schema already describes the coin parameter, but the description adds valuable examples and prefix conventions (e.g., io:NBIS, pm:US500) that help the agent construct valid filter values.

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 clearly identifies a specific resource ('perp futures') and lists the exact data returned (price, 24h change, funding rate, open interest, 24h volume). It is immediately distinguishable from sibling tools like get_price or get_fx_rates.

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 clearly states the supported asset class and sources (Hyperliquid and HIP-3 dexes), making it obvious when to use this tool. It does not explicitly say when not to use it or point to alternatives like get_price, hence not a 5.

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