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

No annotations are supplied, so the description carries the full burden. It does disclose a genuinely behavioral detail not in the schema: the free-trial quota of 5 calls per signed wallet, which is valuable for an agent budgeting tool calls. It stops short of describing what the response looks like (per-statistic fields? single aggregate?) or how failures/costs are signaled, leaving meaningful gaps for a no-annotation tool.

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 sentences with the core purpose front-loaded and no filler prose. The emoji pricing note is slightly off-purpose for a capability description but is compact and informative.

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 whose only parameter is an undocumented string and which has no output schema, the description should state the accepted input format and what the result contains. Neither is present, so an agent must guess how to pass the numbers and what it will get back, even though the computation itself is simple and low-risk.

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% for the single 'numbers' parameter, which is typed only as a string. The description never explains the required encoding — comma-separated list, JSON array literal, whitespace-delimited — nor whether an empty value is allowed despite zero required parameters. This is the biggest practical gap, since an agent cannot reliably construct a valid call from the definition.

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 specific statistics (mean, median, variance) under a 'Statistical utilities' umbrella, so the agent knows roughly what computation happens. However, it does not distinguish this tool from the many siblings that compute the same things individually (x402-mean-of, x402-median, x402-variance, get_stats), which leaves the selection ambiguous in a very crowded namespace.

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 pick this multi-stat tool over the single-stat siblings, no input-format expectations, and no note on limits or edge cases. The only contextual sentence is about pricing ('5 free trial calls per signed wallet'), which tells the agent about cost but not about appropriate usage.

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