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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds material context the annotations do not: this is a paid call at $0.005 USDC via x402, and the response includes a grade and remediation steps. It stops short of noting rate limits or what happens on an unresolvable domain.

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?

Two sentences, zero filler, and the scope is front-loaded before the cost constraint. The long check list is dense but every item conveys distinct scope information.

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 read-only, single-parameter tool with no output schema, the description covers purpose, deliverable, and the payment requirement, so an agent can call it correctly. Only the accepted domain format and edge-case behavior (invalid/unreachable domains) remain unstated.

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?

There is one parameter, 'domain', with 0% schema description coverage and no clarification in the description about expected format (bare domain vs URL vs subdomain). The parameter is largely self-evident from the tool name, which mitigates but does not fully compensate for the gap.

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 ('Domain and email security audit') and then enumerates the exact checks performed (SPF, DMARC, DKIM, MX, DNSSEC, CAA, HTTPS, HSTS, headers, redirect) plus the deliverable (a grade and fixes). That enumeration clearly separates it from generic siblings like domain, dns, certs, or report_domain.

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 exclusions, and no named alternative for overlapping tools such as dns, http_inspect, or report_domain. The only selection-relevant hint is the cost note, which tells the agent it is not a free call but not when it is the right call.

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