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

The annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the definition of premium index, which is helpful context, but does not disclose additional behavioral traits such as pagination, rate limits, or data ordering. Thus, it adds some value beyond annotations but not extensive.

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 a single, well-structured sentence that directly explains the tool's function without redundancy. It earns its place by adding the premium index definition, which is essential for understanding.

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 read-only nature, clear purpose, and full schema coverage, the description adequately supports agent selection and invocation. The term 'history' implies a time-series return, and the schema covers the time parameters, making the combination sufficient. No output schema exists, but the simple concept does not require further explanation.

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 provides descriptions for all six parameters, achieving 100% coverage. The description itself only highlights the required 'contract' parameter and does not add syntax, format, or default behavior details beyond the schema. Therefore, it meets the baseline but does not go beyond it.

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 action ('Get'), the specific resource ('premium index history'), and the target ('for a contract'). It further defines premium index as 'mark price minus index price', which distinguishes this from sibling tools like funding rate or candlesticks. This is specific and unambiguous.

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 retrieving premium index history but does not explicitly explain when to use this tool over alternatives or mention any exclusions. While the context is clear, there is no comparison to sibling tools like funding rate or candlestick endpoints, so usage guidance is minimal.

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