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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: results are returned in input order and each item consumes one check, which hints at quota/billing accounting. It stops short of explaining error behavior for malformed items or rate limits.

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?

Three short sentences with the batching constraint and limit front-loaded, and every clause carries information (use cases, ordering, per-item counting). The opening clause partly duplicates the title's 'up to 100' phrasing, a minor redundancy.

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?

With no output schema, the description should carry more of the return-value burden; it states ordering but not what a result per item looks like (verdict values the sibling report_wrong_verdict implies) or how invalid entries are reported. The basic call contract is clear, but an agent lacks the full picture.

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 both items and policy are already documented in the schema, including the enum values and default for policy. The description only restates the items limit, adding no syntax or format detail beyond what the schema provides.

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 states a specific verb+resource (check up to 100 email addresses and/or domains) and its batching nature implicitly separates it from the single-item siblings check_email and check_domain. It never names those siblings, so the 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?

It names concrete scenarios (lists, CRM exports, lead qualification), which implies bulk use, but gives no explicit guidance on when to prefer this over check_email/check_domain or when a batch is inappropriate. Usage is implied rather than directed.

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