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

No annotations exist, so the description carries the full behavioral burden. It discloses the formula (max minus min) and that an array is required, but says nothing about return format, handling of empty or single-element arrays, non-numeric values, or error behavior. Notably, the input schema is an empty object while the description demands a 'values array' — a gap the description never resolves.

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 16 words across two sentences and front-loads the definition and formula before the input instruction. The 'Range:' prefix echoes the tool name and adds little, but overall there is 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?

For a tool with an empty schema, no annotations, and no output schema, the description is incomplete. It never explains how to pass the array given the schema declares no properties, what the result looks like, or how this differs from the near-duplicate range-stat and range-statistic siblings. An agent cannot reliably invoke this tool correctly from the available information.

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?

With zero parameters, the schema provides no input information at all, so the description's 'Provide values array' is the only guidance an agent has about what to send. It adds real meaning by naming the expected input shape. It could be stronger by specifying the element type (numeric array) or format, but it clears the baseline-4 bar.

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 names a specific verb and resource: 'Calculate the statistical range of a dataset: maximum minus minimum.' The formula makes the operation unambiguous. However, lookalike siblings x402-range-stat and x402-range-statistic exist, and the description does nothing to differentiate from them, so it falls short of a 5.

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 gives no when-to-use guidance and names no alternatives. With siblings like get_stats, x402-range-stat, x402-range-statistic, and x402-midrange covering overlapping statistical territory, an agent gets no help routing to this specific tool. 'Provide values array' is an input instruction, not usage context.

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