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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds genuinely non-obvious behavior: it is data-only, bad input is free, calls resolving under 2 venues are not charged, and payment is required via x402 in _meta['x402/payment'] at $0.003 per successful call. That payment/auth requirement is critical context an agent cannot get from annotations or schema. It stops short of describing response shape or rate limits.

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 core purpose is front-loaded, but the body is a long run-on sentence mixing venues, metrics, keyword-like filler ('Crypto futures basis for BTC, ETH and more') and pricing. The keyword line and the redundant restatement of scope do not earn their place.

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-parameter, read-only tool with no output schema, the description is largely complete: it enumerates the metrics returned and the venue set, and discloses the payment model. Only the response structure and per-venue failure behavior remain unspecified, which is a minor gap.

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 coin parameter already documents accepted aliases (BTCUSDT, XBT, 1000PEPE, kPEPE). The description only reinforces the single-coin scope, adding no format or normalization detail beyond the schema, so the 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 states a specific resource and scope: futures basis and term structure for one coin, covering dated futures across named venues with days to expiry, basis vs index and annualised basis, plus perp premium and predicted funding. It clearly distinguishes itself from the screener/scan siblings by the 'one coin' scope, though it never names those siblings 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?

Usage is only implied: 'one coin' signals a per-coin lookup rather than a market-wide scan, and the pricing note ('under 2 venues not charged') hints at thin-data outcomes. There is no explicit statement of when to choose this over derivatives_snapshot or perp_funding_rates, which cover overlapping territory.

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