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

No annotations are supplied, so the description carries the whole burden. It discloses only a billing trait ('5 free trial calls per signed wallet') and says nothing about return shape, how ties in the mode are handled, input formats, or error behavior. The pricing note is genuinely useful context beyond structured fields, but it is the only behavioral 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?

Two short lines with the functional statement front-loaded; nothing is padded. The emoji and free-trial line are marketing rather than definitional, which costs a point, but they are brief.

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 two undocumented, non-required, ambiguously named parameters and no annotations or output schema, the description leaves too much unresolved: which parameter to use, what format each accepts, and what comes back. The free-trial line does not compensate for that.

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% and neither 'data' nor 'values' is explained. The description offers no clue about the difference between the two parameters, whether one takes a delimited string and the other a list, or which is preferred. With zero required parameters the agent must guess entirely.

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 gives a specific verb and resource: 'Compute the mode of a dataset.' This distinguishes it from statistical siblings such as x402-median, x402-mean-of and x402-stddev by naming the statistic. It does not explicitly reference those siblings, so a 4 rather than 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 purpose implies when to use it: when you need the most frequent value in a dataset. However, there is no explicit guidance on when to prefer this over other centrality tools, no mention that the two parameters are alternatives, and no prerequisite or data-format guidance.

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