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

Annotations already mark this as read-only, idempotent, and non-destructive; the description adds a per-call cost of $0.001 USDC and the fact that the response is byte-identical to a specific Deribit GET endpoint. This is useful operational context beyond the annotations. No contradictions with annotations.

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 short sentences, each carrying distinct information: what the data is, what it costs, and what endpoint it matches. No redundancy or filler.

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, an idempotent/read-only annotation set, and all three optional parameters documented in the schema, the description covers the remaining operational details: cost, endpoint identity, and scope flexibility. Nothing an agent needs to call the tool correctly is missing.

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?

The schema already documents all three parameters with constraints and defaults (100% coverage), so a baseline of 3 applies. The description adds a concrete byte-identical query string example, clarifying how the parameters combine, and reinforces the family choice with 'perpetuals only or the whole listed futures set'. This lifts it slightly above baseline.

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 the exact payload ('tick size, contract size, min trade amount, max leverage, fee rates, state and expiry') and scope ('perpetuals only or the whole listed futures set'), and anchors to a GET endpoint. It clearly distinguishes from other market_* siblings by exchange and data type. The absence of an explicit verb is compensated by the 'GET' endpoint reference.

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?

Provides clear context: it returns Deribit instrument contract rules and lets the agent choose between perpetuals and all listed futures via the family parameter. It does not explicitly name alternatives or exclusion conditions, but the scope and endpoint identity are enough to select this tool over other exchange-specific instrument specs.

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