Verify a batch of email addresses

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. It notes the synchronous nature and return of per-address verdicts, but does not mention credit consumption, rate limits, or whether the operation is read-only. This is a mid-level disclosure: some useful context is provided, but significant behavioral aspects remain unspecified.

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 two sentences, front-loaded with the core purpose, and includes both return behavior and size guidance. Every sentence contributes value, with no filler or 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?

Given the absence of an output schema, the description explains that a per-address verdict is returned, which provides a basic understanding of the results. It also covers scale limits and suggests an alternative for large batches. However, it does not elaborate on the exact verdict structure or how the exclude_* parameters affect results, leaving some gaps. Still, for a tool of this complexity, it is reasonably complete.

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 parameters are already well-documented. The description adds no additional parameter details beyond the schema; it only reiterates the 'list of email addresses' concept. Thus the baseline score of 3 applies, as the description does not go beyond schema-provided semantics.

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 clearly states the tool verifies a list of email addresses synchronously, and explicitly distinguishes itself from the bulk async endpoint for large lists. The verb 'verify' and resource 'list of email addresses' are specific and unambiguous.

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 description provides explicit guidance on when to use this tool ('best for up to a few hundred') and when to use an alternative ('For very large lists use the bulk async endpoint instead'). This directly addresses usage context and alternatives.

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