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

No annotations are provided, so the description bears the full burden of behavioral disclosure. It fails to indicate inputs, outputs, side effects, error behavior, or any operational trait. 'Mean of harmonic' conveys no behavioral information and is not a meaningful disclosure.

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 extremely short, which could be seen as concise, but it is under-specified rather than efficiently informative. It fails to earn its place by adding no usable content beyond the tool name.

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 computing a statistical measure, the absence of input specification, output format, and usage context makes it impossible for an agent to determine how to invoke it correctly. The empty schema and minimal description leave the invocation contract entirely unexplained.

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 tool has zero parameters and the schema is empty, so there are no parameter semantics to document. The baseline of 4 applies because the description cannot add meaning where no parameters exist, though the ambiguity about how the tool receives data remains unaddressed.

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 'Harmonic Mean: Mean of harmonic.' essentially restates the tool name without explaining what the tool actually computes. It is a circular pseudo-definition that does not distinguish this from sibling tools like x402-geometric-mean or x402-mean-of, and it arguably mischaracterizes the harmonic 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?

There is no guidance on when to use this tool versus alternatives, no context, and no exclusions. An agent is given no information about the appropriate scenario for choosing harmonic-mean over any other statistic tool.

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