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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile is covered. The description adds genuinely non-redundant context: a per-call price of $0.008 USDC and the existence of a masked free tier that an API pass or EIP-3009 payment signature unlocks. It does not explain what the masked result omits, which keeps it out of 5 territory.

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?

It is a single front-loaded sentence, which is structurally fine, but it is dense keyword-style copy ('Open Interest & Crowded Positioning Radar') with marketing cadence rather than tight prose. Every clause is topical, but the wording could be leaner.

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 key returned metrics (APR basis spread, open interest, crowded positioning), so an agent knows the payload shape. Annotations cover safety, and all parameters are documented in the schema, so the definition is largely complete; only return granularity/pagination and the masked-vs-unmasked difference are unspecified.

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 limit, symbol, x_api_key, and payment_signature are already fully documented in the schema. The description adds no additional parameter semantics beyond echoing the pricing/unmasking concept. 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?

Names a specific resource (cross-exchange perpetual funding rate arbitrage across Hyperliquid and dYdX v4) and enumerates the returned metrics (annualized basis spread APR, open interest, crowded positioning). This clearly distinguishes it from siblings like defi_yields, kalshi_polymarket_arb, and prediction_markets, which cover different venues/instruments. It stops short of 5 because it is a noun-phrase label rather than a stated verb+action.

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?

There is no statement of when to use this tool versus alternatives such as defi_yields or kalshi_polymarket_arb, and no exclusions or prerequisites are given. The only implicit guidance is the price tag and the parameter descriptions, which is not usage guidance.

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