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

With no annotations, the description carries the full burden and does substantial work: it discloses the exact cost ($0.01 USDC on Base eip155:8453), the payment mechanism and the parameter path (params._meta["x402/payment"]), and the underlying HTTP method and URL. It omits failure modes, output format, and whether payment is taken on error, keeping it short of a 5.

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?

One dense sentence, front-loaded with the returned data, followed by cost and transport details in priority order. No filler, though the compact packing of pricing and URL into the same sentence slightly blurs the distinction between description and invocation metadata.

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 lookup with no output schema, the description covers what is returned, what it costs, and how the payment is supplied — enough to call it correctly. The remaining gap is input format for 'domain', which is the one thing an agent could still get wrong.

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 'domain' parameter has no description or type detail beyond 'string'. The description only says 'for any domain', which does not clarify expected format (bare domain vs. scheme/URL, subdomain handling, IDN) or whether it is optional at runtime despite 0 required parameters.

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 the specific resource (DNS records plus RDAP registration facts) and enumerates the record types and fields returned, so an agent knows exactly what it gets. It is not explicitly distinguished from domfacts__dns or domain_intel__dns, but the combined DNS+RDAP scope implicitly separates it from the DNS-only siblings.

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: an agent can infer this is the tool for looking up a domain's records and registration data, and the pricing/payment note tells it what a call costs. There is no explicit when-to-use, when-not, or named alternative (e.g., domfacts__dns for DNS alone), so routing between the near-identical siblings remains guesswork.

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