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

No annotations are supplied, so the description carries the full burden. It usefully discloses the monetization behavior ('5 free trial calls per signed wallet'), which is real behavioral context an agent would otherwise lack, and the examples reveal output shape. It does not say whether the operation is pure/local computation, what happens after the free calls are exhausted, or how errors surface.

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 compact sentences, front-loaded with the tool's function and immediately followed by illustrative output examples. The emoji-prefixed trial notice is slightly off-register but short and informative rather than padding.

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?

This is a simple two-parameter, no-output-schema tool, so the description need not do much. Still, for an ambiguous-input formatter the missing detail on accepted date formats and reference point (relative to now, or to a supplied baseline) is a real gap an agent would have to guess at.

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% and both parameters are untyped strings with no descriptions, so the description must compensate. 'Provide date or value' does add the important signal that either field alone suffices, which is not inferable from an all-optional schema, but it never explains the accepted date format (ISO 8601, epoch, natural language) or what 'value' means relative to 'date'.

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 and resource ('Format a date as a relative time string') and gives two concrete output examples ('3 days ago', 'just now'), so an agent immediately knows what it produces. It does not, however, distinguish itself from closely named siblings like x402-relative-time, x402-days-since, or x402-time-until, so selection still relies on name matching.

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 by the function of the tool: supply a date, get a relative string. There is no explicit when-to-use guidance, no mention of when to pick x402-relative-time or x402-days-since instead, and no statement of prerequisites or constraints.

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