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 the data source (RDAP), the returned fields, and the payment/auth model (5 free calls per signed wallet), which is useful. It says nothing about invalid-domain handling, rate limits, or latency.

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?

Purpose is front-loaded in the first clause and the sentence is reasonably tight. The trailing emoji free-trial pitch is marketing clutter that slightly dilutes an otherwise efficient line.

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?

There is no output schema, so describing the return values is genuinely helpful, and the RDAP source is disclosed. But with 0% parameter documentation, no annotations, and an unexplained second parameter, the definition is not complete enough to guarantee a correct call.

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% for two parameters, so the description must compensate and does not. It implies a domain is supplied but never explains the `domain` param format, nor the unexplained `input` parameter.

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 (fetches) + resource (RDAP expiration event for a domain) and even names the return contract (days remaining, expired flag). This differentiates it from neighbouring domain tools like x402-domain-age or x402-whois, though it never explicitly contrasts with them.

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 when-to-use guidance, no mention of alternatives (e.g. domain-age for registration date, whois for full records), and no prerequisites such as domain format. The only extra context is a pricing note about free trial calls, which does not help tool selection.

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