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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety. The description adds valuable behavioral details beyond that: a per-call cost of $0.001 USDC and byte-identical equivalence to a specific REST endpoint. These are not in annotations and meaningfully inform usage.

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 sentences, no fluff, and the core purpose is front-loaded. The cost and endpoint equivalence are added efficiently without repetition. Every clause earns its 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?

The tool is simple (one optional parameter), has an output schema, and annotations cover safety. The description supplies purpose, cost, and an exact endpoint reference, leaving nothing essential missing for an agent to call it correctly.

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 input schema already documents the single optional parameter indexName with its description and default value, and schema coverage is 100%. The description does not add further parameter-level detail (e.g., allowed values or format), so it does not exceed the baseline of 3.

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 clearly states the tool returns Deribit's own index price plus the estimated delivery price it settles against, and frames it as the reference for funding/settlement checks. This distinguishes it from sibling tools like market_deribit_funding_window (funding rates) and market_deribit_volatility_index (volatility). The verb is implicit but the resource and scope are precise.

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?

It gives a concrete use case (funding/settlement checks) and notes it is the authoritative index price. However, it does not explicitly say when not to use it or name alternative tools for similar data, so it falls short of an explicit exclusion. The context is clear enough for an agent to infer suitability.

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