validate_email

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

No annotations are provided, so the description must carry the full burden. It discloses the main behavior and output fields (deliverability status, spam risk score, SMTP verification result, send recommendation), but it does not mention any side effects, network dependencies, or whether the tool is read-only. This is adequate but lacks deeper context.

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 a single, tightly-worded sentence that front-loads the key action and outcome. Every claim (single address, return types) earns its place, 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?

For a simple, single-parameter tool with no output schema, the description is fairly complete: it states the purpose and enumerates the return values. It could add usage guidance or mention edge cases, but the core information is present and sufficient given the tool's simplicity.

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?

The schema fully describes the only parameter ('email' with 'The email address to validate'), giving 100% coverage. The description adds no extra meaning about the parameter format, constraints, or example values, so the baseline score of 3 is appropriate.

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's function: 'Validate a single email address' with a specific verb and resource. It also distinguishes itself from the sibling tool 'validate_emails_bulk' by explicitly limiting scope to a single address, making the purpose 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 phrase 'a single email address' provides clear context that this tool is for individual validation, not bulk operations, which helps differentiate from the sibling 'validate_emails_bulk'. However, it does not explicitly name the alternative or state when-not-to-use, so it falls short of a full 5.

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