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

With no annotations, the description must cover behavioral expectations itself. It discloses authentication/payment requirements and the window default/max, which is useful, but it does not explicitly state that this is a read-only computation, what the response contains beyond what the output schema implies, or any rate-limit/error behavior.

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 not front-loaded: the long payment/auth sentence appears before the actual purpose, burying the core function. The payment details are specific but lengthy, and the structural priority is inverted.

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 simple single-parameter tool, the description covers the core computation, payment/auth requirements, and window constraints. However, it never identifies which nine chains are meant, lacks any usage context, and relies on the output schema to explain the return shape—acceptable but not complete guidance for an agent.

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 provides only a bare 'number' type for window with no description, so the description must compensate. It does by specifying units ('in days'), a default of 7, and a max of 30. This is meaningful added semantics, though a minimum value and optionality are not stated.

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 phrase 'Pairwise correlation of hourly returns across the nine chains' clearly identifies the operation and resource, even though it lacks an explicit imperative verb like 'Compute.' It is distinguishable from most sibling tools by its correlation-focused computation, but it does not explicitly contrast itself with similar market-analysis tools.

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 provides operational prerequisites (API key or per-call payment) and a parameter constraint, but gives no guidance on when to choose this tool over alternatives or when not to use it. There are no references to sibling tools or use-case conditions.

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