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

With no annotations, the description carries the full burden, and it does disclose the exact DNS name constructed, the returned fields (hasDKIM, up to 300 chars of record), and the payment model (5 free trial calls per signed wallet). It still omits error behavior for missing records, rate limits, and whether a signed wallet is required for all calls.

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 front-loaded sentence carries purpose, query mechanics, and return fields, with the pricing tag kept to the end. No sentence is wasted.

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, but the description names the return values (hasDKIM plus truncated record text), and the query semantics are clear, so an agent has what it needs for a simple lookup. Minor gaps remain around auth requirements and the unexplained 'input' parameter.

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%, so the description must compensate. It effectively explains two of the three parameters by spelling out the 'selector._domainkey.domain' construction, giving domain and selector concrete meaning, but the third parameter 'input' is left entirely undefined in both schema and description.

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 ('Looks up the DKIM TXT record') and pins the exact query pattern (selector._domainkey.domain), so an agent can tell it apart from x402-dmarc-check, x402-spf-validate, and generic x402-txt-lookup without opening any schema.

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?

No when-to-use guidance and no routing among the many sibling DNS/email-security tools (dmarc-check, spf-validate, txt-lookup, mx-lookup). The pricing note implies a paid x402 context but says nothing about when this lookup is the right call versus its alternatives.

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