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 return shape (hasDMARC plus joined record) and surfaces payment context ('5 free trial calls per signed wallet'), which is useful. However, it omits error behavior for missing/invalid domains and any rate-limit detail beyond the trial note.

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?

Front-loaded in a single efficient sentence with the return value immediately following the action. The emoji and free-trial marketing clause add minor noise, but the core is tight.

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?

No output schema exists, and the description reasonably covers the return contents, so that gap is closed. But the ambiguous dual-parameter surface (input vs domain, neither required, 0% documented) is left unresolved, leaving an agent guessing how to call it correctly.

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% for two parameters. The phrase 'of a domain' hints the domain param is the target, but the second parameter 'input' is never explained and it is unclear which parameter is authoritative or how they relate.

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: 'Resolves the _dmarc TXT record of a domain and returns hasDMARC plus the joined record.' The named record type inherently distinguishes it from DNS siblings like x402-dkim-check or x402-spf-validate, though it never explicitly names an alternative.

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?

The description explains what happens but never states when to use this versus the many adjacent DNS/email-security tools (dkim-check, spf-validate, txt-lookup, dns-record). No prerequisites, exclusions, or alternatives are given.

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