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

With read-only and non-destructive annotations already covering safety, the description adds meaningful behavioral context: status values, the stability of results_so_far, and that results are deleted 7 days after the check. It does not mention auth or rate-limit behavior, but the retention and state-transition notes are useful beyond the annotations.

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?

The description is dense but front-loads the resource being fetched and then covers status, credits, addresses, in-progress fields, retention, and the results flag. It is appropriately sized for a no-output-schema tool, though the long parenthetical field list is somewhat run-on.

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?

Because there is no output schema, the description carries the burden of explaining the returned shape, and it does so for statuses, credits, addresses, results_so_far, answered, and pending. Some fields like counts are only named rather than explained, so it is strong but not fully exhaustive.

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 description coverage is 100%, so the check_id, results, and passport_token parameters are already documented. The description repeats that 'results: false leaves them out' but adds little or no semantic detail beyond the schema's own text.

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?

The description makes clear this is for a single email check by starting with 'One email check' and enumerating the status, credits, and address results it returns. It is specific about the resource and payload, though it does not use an explicit verb like 'retrieve' or directly contrast itself with list_email_checks/get_sender_check.

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 single-check framing and by explaining the 'while checking' versus completed states, but there is no explicit when-to-use guidance or named alternative. It does not say, for example, to use this after check_emails or instead of list_email_checks.

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