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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered. The description adds that it returns current price and 24h change and supports filtering, which is useful but does not go beyond annotations to disclose rate limits, pagination, or other behavioral traits. No contradiction is present.

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 description is two sentences, front-loaded with the core purpose, and every word contributes. It is efficient and free of filler, making it easy for an agent to parse quickly.

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?

Given the tool's low complexity (2 optional params, read-only, output schema present), the description covers purpose, parameters, and data source. It omits explicit behavior when no filters are provided, but that is reasonably implied. The output schema handles return details, so this is largely complete.

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 0%, so the description must compensate. It explains both parameters: quoteCcy for filtering by currency (with 'USD' example) and instId for a specific instrument. This adds meaning beyond the bare schema and clarifies intended usage, though it is concise and does not elaborate on edge cases or mutual exclusivity.

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 provides current index price and 24h change for OKX index instruments. It distinguishes from generic ticker tools by explicitly mentioning 'index instruments', but unlike the high-scoring example, it does not name a sibling tool or explicitly contrast with alternatives.

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 description implies usage for index instruments and explains filtering by quote currency or instId. However, it does not provide explicit when-to-use versus alternatives, such as the regular 'ticker' or 'tickers' tools, nor does it state exclusions or prerequisites. Usage guidance is implied rather than explicit.

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