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

With no annotations, the description carries the full behavioral burden, and it does disclose the exact return payload (week count and leap-year flag). It adds the x402 payment context (5 free trial calls per signed wallet), which hints at a metered/auth-gated service, but says nothing about error behavior, validation of the year, or what happens with an invalid input.

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 definition is short and the core purpose is front-loaded, which is good. The trailing emoji/pricing sentence about free trial calls does not help an agent invoke the tool and is effectively promotional filler, so not every sentence earns its place.

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 stateless computation with no output schema and no annotations, the description adequately explains the result. It falls short on the undocumented 'input' parameter and on distinguishing this tool from its many week-related siblings, leaving the agent with a workable but incomplete picture.

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 two parameters, so the description must compensate and largely does not: it implies a year argument but gives no format (string type, range, negative years?), and the second parameter 'input' is never mentioned at all. Only one of two parameters is even indirectly explained.

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 a concrete output — the ISO week count (52 or 53) plus a leap-year flag — for a given year, so the resource and return are unambiguous. However, it does not distinguish itself from near-identical siblings such as x402-weeks-in-year, x402-week-number, or x402-iso-week, so an agent has no basis to prefer this tool.

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 several sibling week-count tools, nor any prerequisite or exclusion. The only 'usage' text is a promotional note about free trial calls, which does not guide selection.

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