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 payment model ('5 free trial calls per signed wallet'), which an agent needs for a paid x402 endpoint, but it says nothing about the result shape (years only? years/months/days?) or edge-case handling such as future dates or invalid formats.

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 short sentences, front-loaded with the purpose. The 'Age:' prefix slightly duplicates the tool name and title, but the free-trial note is worthwhile for a metered endpoint, so there is little waste.

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 calculator with no output schema, the description should at minimum pin down the date format and the meaning of the returned age. It omits both, and offers no differentiation from the near-identical sibling, so it is adequate but not fully self-sufficient.

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 for the single parameter is 0% — the schema just declares dob as an untyped string with no description. The description partially compensates by telling the agent dob means date of birth, but it gives no accepted syntax (ISO 8601, MM/DD/YYYY, epoch), leaving the most important ambiguity for this parameter unresolved.

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?

States a specific verb and resource: 'Calculate age from a date of birth.' An agent knows exactly what it computes. It does not, however, distinguish itself from the sibling x402-age-calculate (or x402-account-age / x402-domain-age), so an agent facing the flat sibling list has no signal about which age tool to pick.

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 input ('from a date of birth'). There is no statement of when to prefer this over x402-age-calculate, nor any prerequisite or exclusion. The free-trial line addresses cost, not selection.

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