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

With no annotations, the description does carry the behavioral burden, and it usefully discloses the calculation formula plus a payment/auth detail ('5 free trial calls per signed wallet'). However, it does not explain input parsing, validation behavior, or what is returned for unusual datasets.

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 short and front-loads the core calculation before the payment note. The repeated 'Midhinge: Calculate the midhinge' wording and free-trial emoji are minor inefficiencies, not a structural problem.

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 statistical calculator, the formula and parameter name are enough to convey the broad intent. But the lack of a proper input format—especially given the string-vs-array mismatch—leaves a real gap for correct invocation.

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 0%, so the description must compensate. It identifies the single parameter as 'values array', but the schema declares it as a string, creating ambiguity rather than clarifying format, delimiters, or accepted syntax.

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?

It states a specific verb and resource ('Calculate the midhinge') and defines the statistic as the average of Q1 and Q3. The purpose is clear, but it does not distinguish this tool from closely related siblings such as x402-quartile, x402-iqr, or x402-interquartile-mean.

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 says to 'Provide values array' and mentions a free trial, but gives no when-to-use guidance, prerequisites, or comparisons to similar statistics tools. An agent must infer that this is the right tool rather than x402-interquartile-mean or x402-midrange.

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