Emails Validator

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

With no annotations, the description carries the full burden of behavioral disclosure. 'Validate' strongly implies a non-mutating check, which is helpful context, but the description doesn't explicitly explain the async/webhook execution behavior that the schema exposes. It also leans on 'documented endpoint' rather than stating important operational details inline.

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 compact and front-loaded: one lead sentence stating the action and endpoint, followed by a scannable three-item 'Best for' list. Every line earns its place, and no filler is present.

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 straightforward validator with a fully documented schema and an output schema present, the description covers the main use cases and purpose. It could be marginally more complete by noting rate/cost implications or the deprecated async flag, but nothing essential is missing for selecting and invoking the tool.

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?

Input schema coverage is 100%, and each parameter already has a meaningful description (query, async, webhook, execution_mode). The tool description doesn't need to restate parameter meanings; the baseline 3 applies because it adds no extra parameter-level insight beyond the schema.

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 opens with a specific verb-resource pair ('Validate email addresses') and names the exact endpoint, then reinforces the purpose with three concrete use cases. This clearly separates it from sibling tools like emails_and_contacts, which are about finding/collecting emails rather than checking validity.

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 'Best for' bullets give clear contexts (deliverability checks, lead-list validation, pre-enrichment filtering) that tell an agent when to choose this tool. It doesn't explicitly say when not to use it or name alternatives, so it stops one step short of a 5.

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