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 useful behavior: resolution happens over DNS (a live network call that can fail), results come back sorted, and access is metered at '5 free trial calls per signed wallet', which implies a wallet signature is required. It omits error/empty-result behavior and any rate or timeout details.

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 tight sentence front-loads the action and resource, with the pricing note appended. No filler, though the promotional fragment is not operationally useful to an agent.

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 lookup tool with no annotations, no output schema, two completely undescribed parameters, and no required-parameter declaration. The description should have clarified the 'input' vs 'domain' distinction and the failure mode for domains with no CNAME record; neither is covered.

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 ('input' and 'domain') are undocumented in the schema. The description implies a domain argument but never explains the ambiguous 'input' parameter or how the two relate; an agent has no basis for choosing between them.

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+resource: 'Resolves a domain's CNAME records through DNS'. An agent can tell it does CNAME resolution rather than generic DNS. However, it never distinguishes itself from the many DNS siblings (x402-dns, x402-dns-lookup, x402-dns-record), so it stops short of a 5.

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 when-not to use it, and no routing to or from the numerous DNS alternatives such as x402-dns-all or x402-mx-lookup. Usage is only implied by the tool name and the word 'CNAME'.

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