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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses the return value ('returns the value at that decile boundary'), which tells the agent this is a boundary lookup rather than a full decile classification. It says nothing about edge cases (fewer than 10 values, ties, interpolation method), which matter for a statistical tool.

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 short sentences, front-loaded with the action and followed by the required inputs and the return. Minor redundancy between the 'Decile:' label and 'Calculate a decile', but no wasted prose.

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?

With no output schema and no annotations, the description is the only source of behavioral information. It covers the return value and the decile range, but leaves the input serialization (a string-typed array) and edge-case behavior undefined, which is a real gap for a computational tool with ambiguous parameter types.

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 coverage is technically 100%, but the schema descriptions are placeholders ('Decile to process', 'Values to process'). The description compensates by stating that 'values' is an array and that 'decile' is bounded 1-10, which the schema does not express. It still leaves the string-typed encoding of both parameters (how an array is serialized) unexplained.

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 specific verb and resource ('Calculate a decile of a dataset') and clarifies it produces the value at a decile boundary, which is more precise than the bare tool name. It does not, however, distinguish itself from close siblings such as x402-quartile, x402-percentile, or x402-iqr, so an agent must infer the difference from names alone.

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?

Usage is only implied: the description tells the agent to supply a values array and a decile 1-10, which signals this is a single-statistic computation. There is no explicit when-to-use guidance, no mention of when to prefer quartile/percentile instead, and no stated prerequisites or limits.

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