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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-redundant behavior: it only touches public DNS records and the public home page (access scope, no credentials), and the report is written in Portuguese — a notable output trait no structured field conveys.

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, front-loaded with the primary email-authentication purpose, then the website-security purpose, then the access-scope and output-language constraints. Every clause carries information an agent would otherwise have to guess.

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 single-parameter, no-output-schema tool with strong annotations, this covers purpose, access scope and output language. The only gap is that it does not sketch what the report contains or how findings are surfaced, which an agent may want when deciding whether this tool answers its question.

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?

With a single parameter at 100% schema description coverage, the schema already explains that 'url' accepts either 'example.com' or 'https://example.com'. The description adds no further parameter meaning, such as whether a bare domain vs full URL with path changes behavior. Baseline 3 is appropriate.

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?

Uses a specific verb ('Checks') with two clearly enumerated resources: domain email authentication (SPF, DKIM, DMARC, mail servers) and website security (HTTPS, headers, WordPress exposure, Lovable/Supabase). An agent immediately knows the scope. It does not, however, distinguish itself from the sibling check_ai_built_app, which plausibly overlaps on the 'Lovable/Supabase setup' portion.

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 diagnostic intent is implied by the enumerated checks and the note that it reads only public records, so an agent can infer this is a non-invasive audit. But there is no explicit when-to-use, when-not-to-use, or routing statement pointing to check_ai_built_app or diagnose_shopify_store, leaving sibling selection to inference.

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