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

With no annotations, the description carries the full burden. It usefully discloses a rate-limit/pricing trait ('5 free trial calls per signed wallet'), which is real behavioral context, but it omits whether the result is relative to today, how timezones are handled, and what happens when neither input is supplied.

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?

A single front-loaded sentence delivers the operation, inputs and format with no filler; only the trailing promo emoji/free-trial clause is marginal but brief.

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 two-param calculator with no output schema, the description adequately conveys inputs and the return shape (years plus elapsed days). It leaves the required-field and precedence questions open, which is the main gap for correct invocation.

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 contributes the expected format (YYYY-MM-DD) and indicates dob and birthdate are interchangeable inputs, but does not say which takes precedence if both are sent or whether either is required (schema marks neither required).

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 ('Computes age in whole years and elapsed days') and names the accepted inputs, so the operation is unambiguous. It does not differentiate from close siblings such as x402-age or x402-account-age, which the agent must disambiguate on its own.

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?

It implies the tool is for age computation but never states when to choose it over x402-age, x402-account-age, or x402-days-since, nor any prerequisites. No exclusions or alternative-routing guidance is given.

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