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 never states how inputs are parsed (the values param is a string, not an array), whether the output is a single number or structured object, or how it handles empty/insufficient data. 'Returns Q3 minus Q1' is the only behavioral hint.

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 tight sentences, front-loaded with the purpose and followed by the formula and the input requirement. Nothing redundant or padded.

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 single-parameter calculation tool with no output schema and no annotations, the description covers purpose and the basic formula but leaves the return shape, input format for the string parameter, and edge-case behavior unspecified. Adequate but with clear gaps.

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 description coverage is 100%, but the schema's only text is the unhelpful 'Values to process'. The description adds real value by clarifying the parameter is a dataset (values array), implying numeric input, which the schema's bare string type does not convey. Not a full 5 since format/delimiter for the string is still unspecified.

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?

States a specific verb and resource: 'Calculate the interquartile range (IQR) of a dataset', and even spells out the formula (Q3 minus Q1, 75th minus 25th percentile). It is clear and self-contained, though it does not name a sibling (e.g., x402-quartile, x402-range-stat) to distinguish which statistic tool to pick when several are close.

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 when the tool applies by defining IQR, and 'Provide values array' implies the precondition. But with dozens of sibling statistics tools (quartile, percentile, range-stat, quartile-deviation), it gives no explicit guidance on when to use IQR over those alternatives.

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