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

With no annotations, the description carries the full burden and does most of it: it discloses data freshness (updated hourly), sourcing/provenance (Hyperliquid public data, derived, attributed), coverage cap (100 coins, OI-ranked), and the paid-access model including the exact failure path (unpaid calls return the x402 challenge; pay and retry). What is left out is error behavior beyond payment and any latency/rate limits, which keeps it off 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?

The payload and sign convention are front-loaded, then usage, freshness, and cost, which is a sensible order. It loses a point for redundancy: the $0.001 per-call price is stated in prose and then repeated almost verbatim in the bracketed payment note.

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 one-optional-parameter read tool with no output schema, the description supplies everything an agent needs: what fields come back, how to read the sign, how results are ordered and capped, how fresh the data is, and how to satisfy the payment gate. No material gap remains.

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% and the single `limit` parameter is already documented with its default and cap, so the schema does the heavy lifting. The description adds only the framing that the cap refers to coins ranked by open interest, which is marginal meaning beyond the schema; 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?

The description names a specific verb and resource ('Latest Hyperliquid perpetual-funding snapshot') and pins down the payload precisely: hourly funding rate per coin with sign convention (positive = longs pay shorts) plus derived APR, ranked by open interest. Nothing here overlaps with the Polymarket siblings, so an agent can distinguish it 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?

'Use when an agent needs current perp funding rates for a carry or basis view' gives a concrete triggering scenario rather than a generic 'get funding' framing. It does not name exclusions or alternatives, but the sibling set is a different domain (Polymarket odds/disagreement), so the routing risk is low.

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