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

Annotations cover the read-only/open-world profile, and the description adds meaningful non-annotation context: the data source (Hyperliquid) and, importantly, the per-call cost ($0.002 USDC via x402), which an agent must know before invoking. It does not discuss rate limits, caching, or freshness, but the cost disclosure is genuinely useful.

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 sentences, front-loaded with the resource and source, then the field list, then the selection mode and cost. No filler and the pricing caveat is placed where an agent will read it.

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?

No output schema exists, but the description enumerates the returned metrics (mark/oracle price, 24h change, funding, OI, volume, premium, max leverage), effectively covering the return shape. Combined with cost and both parameters, an agent has enough to call it correctly; only freshness/rate-limit behavior is unstated.

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%, so the schema already documents 'coins' (comma list, omit for top by volume) and 'limit' (1-200, default 20). The description's 'Pick coins or get the top markets by volume' paraphrases the schema rather than adding format or edge-case detail, 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+resource ('Perpetual futures market data from Hyperliquid') and enumerates the exact fields returned, which distinguishes it from narrower siblings like perps_funding and oracle_price. It never names a sibling explicitly, so the differentiation is inferable rather than stated.

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?

'Pick coins or get the top markets by volume' gives implied usage for the two modes of this tool, but there is no when-to-use/when-not guidance and no routing to alternatives such as perps_funding when only funding is needed. Usage is inferable but not spelled out.

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