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

With no annotations, the description carries the full burden, but it does disclose commercially relevant behavior ('5 free trial calls per signed wallet'). It says nothing about authentication requirements beyond 'signed wallet', error behavior, or return format, so disclosure is partial but not absent.

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?

A single front-loaded sentence delivers the predicate definition, followed by a short pricing note. The emoji and promo text add minor noise but cost little.

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 trivial one-parameter predicate with no output schema, the mathematical definition is arguably enough, and the cost note is helpful. Still missing is any statement of the return value shape or the distinction from the duplicate sibling tool.

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 coverage is 0% and the single 'value' parameter has no description. The phrase 'sum of its digits' implicitly conveys that value is treated as a number or numeric string, which adds some meaning, but format constraints (integer only? leading zeros? negative values?) remain unstated.

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 states a specific check (whether a value is a Disarium number) and even spells out the mathematical rule, so the agent knows exactly what predicate is evaluated. It does not, however, distinguish itself from the near-identical sibling x402-is-disarium-number, leaving duplicate-selection ambiguous.

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 statement of when to call this versus the many other number-property tools (x402-is-disarium-number, x402-is-narcissistic-number, etc.) or what it returns. The only contextual hint is the pricing line, which is not usage guidance.

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