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

With no annotations, the description carries the full burden; it does disclose default behavior (no date = current year) and the time component of the result, plus the pricing/paywall signal ('5 free trial calls per signed wallet'). It omits timezone handling, accepted date formats, and output type (unix vs ISO), which matter for a timestamp 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 tight sentences with the core behavior front-loaded and the fallback case immediately following. The emoji trial-call footer is promotional rather than functional, which is a minor deduction but not enough to hurt readability.

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 one-parameter tool with no output schema, the description covers the essential behavior and default. However, a timestamp-producing tool that leaves timezone and output format unspecified leaves an agent unable to predict the exact return value, so it is adequate but not 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% and the single parameter has no description, so the description must compensate; it does explain that 'date' is optional and that omitting it defaults to the current year. It never states the expected date string format, leaving a real ambiguity that the schema does not fill.

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 specific verb and resource ('Return the end-of-year timestamp') and pins down the exact value produced (Dec 31 23:59:59), so an agent knows precisely what it computes. It does not distinguish itself from close siblings like x402-year-start or x402-end-of-day, which keeps it below a 5.

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?

Usage is only implied: the tool is for end-of-year timestamps and falls back to the current year when no date is supplied. There is no explicit statement about when to prefer x402-year-start, x402-month-end, or the generic date formatters, so an agent must infer routing.

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