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

With no annotations, the description carries the full disclosure burden and does meaningful work: it reveals the cost and payment mechanism (x402 on Base), and it describes the shape of the result — per-record findings plus 'flags and a verdict' — which tells the agent a synthesized judgment is returned, not raw DNS dumps. It stops short of stating that this is a purely read-only public-DNS lookup with no side effects, and gives no latency, rate-limit, or failure-mode information for a paid call.

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-loads the resource and the checklist of checks, then a second short sentence delivers the price and payment rail. Every clause is a scannable fact — no filler, no restatement of the tool name.

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 the description must convey return content, and it does so reasonably: check inventory plus flags and verdict. Cost and payment method are covered, which matters for a paid tool. What is left out — exact output field names, response format (JSON), and whether checks failing to resolve are reported as errors or as findings — is minor for a single-parameter read tool.

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?

Only one parameter, and the schema already documents it fully ('Email domain, e.g. example.com'), giving 100% coverage. The description adds no syntax, normalization, or IDN/subdomain handling detail beyond that, so the schema does all the work and baseline 3 applies.

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?

Names a specific resource (a domain's email spoofing protection) and enumerates exactly which records are inspected — MX, SPF with recursive lookup count and all qualifier, DMARC tags, MTA-STS, TLS-RPT, BIMI, DKIM selectors — plus a verdict. That enumeration implicitly separates it from domainaudit_tls and domainaudit_headers, but no sibling is ever named explicitly, so differentiation is inferred rather than stated.

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 implied by the subject matter: run this when you need to assess a domain's email anti-spoofing posture. There is no explicit when-to-use/when-not-to-use guidance and no statement about when a caller should prefer domainaudit_audit (the broad audit) over this narrower email-specific one. The one genuine usage constraint given is commercial: $0.003 USDC per call paid via x402 on Base.

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