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

With no annotations, the description carries the full behavioral burden. It usefully discloses the implementation approach ('February 29 probe') and a payment/auth constraint ('5 free trial calls per signed wallet'), but says nothing about error handling or return format for an undocumented output.

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?

Compact single sentence with the core operation front-loaded, followed by a short payment note. No filler or repetition, though the trial-call marketing text is marginally off-purpose.

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 simple boolean check the core intent is covered, but with three undocumented string parameters and no output schema, an agent cannot know how to pass 'input'/'value' or how the boolean is returned. The definition stops short of complete.

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%, so the description must compensate. It clarifies only 'year' and its default; the 'input' and 'value' parameters are completely unexplained, leaving two of three parameters with no meaning anywhere.

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 uses a specific verb+resource ('Checks whether year ... is a leap year'), so an agent immediately knows the operation. It does not, however, distinguish itself from the near-identical sibling x402-is-leap-year-num, leaving that ambiguity unresolved.

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 only guidance is the default value behavior ('default current UTC year'). There is no statement of when to prefer this over x402-is-leap-year-num or other date siblings, and no prerequisites or exclusions.

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