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

With annotations declaring readOnlyHint=false and destructiveHint=true, the description explains *why* it is a mutating call: it spends from the balance ($1 per domain), is rate-limited, and may require owner approval. It also discloses that only public DNS is queried and nothing is sent, and honestly bounds what a pass means (reputation, content, engagement still matter) — context no annotation provides.

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?

Purpose and price lead, then parameters, then limits, then caveats — a sensible front-loaded order with no filler sentences. It is dense and somewhat run-on (long parentheticals and semicolons), which slows scanning but does not waste content.

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, yet the description describes the return shape (score, per-check verdict, plain summary, exact DNS records to add), payment/approval behavior, and rate limits — everything needed to decide and call correctly. The residual caveat about inbox deliverability is a useful boundary rather than a gap.

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 100%, so the baseline is 3, but the description adds real semantics on top: provider 'ADDS that provider's DKIM selectors and return path to the search' and 'the common selectors are always tried too', plus the SES-specific instruction to pass the three Easy DKIM tokens via dkim_selectors. That tells the agent what leaving provider blank costs (wider, slower selector search), which the schema does not.

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?

Opens with a specific verb+resource ('Check how the domain your owner sends email from is set up') and enumerates the nine record types inspected, plus the enumerated deliverable (score, pass/warn/fail per check, exact DNS records). It doesn't explicitly distinguish this purchasing tool from the sibling readers get_sender_check / list_sender_checks, so the agent must infer that this one starts a paid run rather than fetching an existing report.

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?

Gives concrete gating context: $1 per domain from the balance, 30 checks per owner per 24h, one domain at most 5 times an hour, and larger orders land in pending_approval. It also tells the agent how to use the provider parameter (including the Amazon SES three-token case). It stops short of naming the alternative path for retrieving an existing result (get_sender_check/list_sender_checks), which is the one routing decision the siblings create.

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