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

Annotations already declare readOnly and openWorld, and the description adds real context beyond them: the data source (Deribit public book summary), the pricing model ($0.003 USDC per successful call via x402 across Base/Solana/Arc), and the explicit 'failed calls are not charged' policy. That cost/billing disclosure is exactly the kind of thing an agent needs, though freshness/caching behavior and rate limits are unstated.

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?

Two tight sentences: payload first, then exclusions, then price. Nothing is repeated and the most decision-relevant facts (metrics delivered, what is missing, cost) are front-loaded.

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 an output schema present, the description needn't explain return shapes, and it correctly covers data provenance, metric scope, exclusions, and billing. Remaining gaps are minor: no mention of expiry horizon specifics or how stale the book summary can be.

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?

Only one optional parameter with 100% schema description coverage, so the schema already carries the burden ('BTC, ETH or SOL (default BTC)'). The description restates the same asset set without adding format, casing, or behavior for unsupported values, which is the baseline-3 outcome.

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: a Deribit option market summary for BTC, ETH or SOL, with an enumerated metric list (put/call OI and volume ratios, max-pain strike, ATM mark IV, nearest expiries). It is clearly distinguishable from volatility-adjacent siblings like perp_funding_rate_heatmap or leverage_liquidation_levels, though it never names an alternative explicitly.

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 negative scoping is genuinely useful: 'No 25-delta skew (needs per-option greeks, not fetched) and no order flow' tells an agent exactly when this tool will not satisfy a request, before it spends money. It lacks a positive 'use this instead of X' routing statement, so it falls short of a 5.

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