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

No annotations are supplied, so the description carries the burden; it does disclose the return type ('returning a boolean') and reveals a metering/payment trait (free trial calls per signed wallet). It says nothing about error behavior, accepted input range, or whether non-numeric strings are rejected.

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 core sentence is front-loaded and efficient, but the trailing '🆓 5 free trial calls per signed wallet' is promotional filler that consumes space without helping an agent decide or invoke. The redundant 'Is Strong:' prefix also restates 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 single-parameter boolean predicate with no output schema, the description covers the operation, the logical condition, and the return type, which is nearly everything an agent needs. The remaining gap is input format for the string-typed 'value'.

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 schema documents a single 'value' of type string with no description (0% coverage). The description clarifies what that value is — the integer whose digit factorials are summed — which is real added meaning, but it does not specify the accepted string format, sign handling, or size limits for what is typed as a string.

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 precise predicate: 'Checks whether value equals the sum of the factorials of its digits, returning a boolean.' This resolves the ambiguity of the bare name 'is-strong' (which could be read as password/strength checks) and separates it from neighboring predicates like is-perfect or is-armstrong by naming the exact condition. It stops short of 5 only because it never states the term 'strong number' or otherwise ties the predicate to the family of number-property siblings.

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 use this tool versus the many other x402-is-* predicates, nor any prerequisite or input expectation. The only guidance-like text, '5 free trial calls per signed wallet,' concerns payment, not tool selection.

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