email_validator

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

With no annotations, the description carries the full burden and does so well: it discloses cost and billing model (~$0.0005/email billed to your own Apify account), output cardinality (one scored row per address), the DNS-over-HTTPS mechanism, and the key limitation of not probing SMTP mailboxes.

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 capability list and followed by a compact pricing note; both earn their place. Slightly dense but free of filler.

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 tool with no output schema or annotations, the description supplies the return shape (one scored row per address) and the classification dimensions a consumer can expect, plus cost and method. It stops short of enumerating the exact fields in each scored row, which is a minor residual 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 description coverage is 100%, so both the emails array and checkMx flag are already thoroughly documented in the schema (including defaults, examples, and behavior). The description adds no parameter-level detail beyond that, so the baseline of 3 applies.

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 (validates) and resource (list of email addresses) and enumerates the exact checks performed: syntax, MX/A DNS records, disposable/free-provider/role classification, and typo suggestions. It also scopes out what it does not do (no SMTP mailbox probing), so an agent knows precisely what it gets.

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 clear context of use — validating a batch/lead list, one row per address — and a meaningful boundary (no SMTP mailbox probing). It lacks explicit when-to-use-vs-alternative guidance, but the sibling tools are unrelated Apify actors, so there is no real alternative to route against.

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