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

With no annotations or output schema, the description carries the full burden. It discloses the primary behavior (computes and returns the value at the requested decile boundary) but does not cover computational details such as interpolation method, handling of unsorted data, or behavior for invalid decile values. This is adequate for a simple calculation tool but not rich transparency.

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 singht, tightly packed sentence with a leading label, a clear verb, input specification, and output contract. There is no fluff or redundant exposition, and the essential information is front-loaded.

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 tool the description gives the core contract: what to provide and what comes back. However, the empty input schema means the exact parameter key names must be inferred, and the description does not mention the expected type of the values array or the precise decile computation method, leaving some ambiguity. It is mostly sufficient but not fully complete for an agent with no other metadata.

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 is completely empty, so the description is the only source of parameter information. It explicitly identifies two expected inputs: a values array and a decile number with rule 1-10). This fully compensates for the absent schema, going beyond the baseline 4 for zero-parameter tools.

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 states a clear verb and resource: 'Calculate a decile of a dataset', and specifies the output as the value at the decile boundary. It is specific enough to distinguish from related statistical tools like quartile or percentyle by the term 'decile', but it does not explicitly name any siblings or draw comparisons, so it stops short of full differentiation.

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 the usage context: whenever an agent needs a decile boundary, the agent should provide an array and a decile number (1-10). However, it does not state when-not to use this tool, nor does it reccommend alternatives like x402-quartile or x402-percentile for other percentile needs. The guidance is implicit rather than explicit.

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