verify_email

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

With no annotations provided, the description fully carries the burden of transparency. It details every check (syntax, MX, disposable, role, catch-all, deep SMTP probe) and explains behaviors like 'live SMTP RCPT-TO probe' that does not send email, and graceful degradation if port 25 is blocked. No contradictions.

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 front-loaded with the main purpose in the first sentence, uses a well-organized list for the checks, and has no extraneous words. Every sentence adds value, making it highly efficient.

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?

Despite lacking an output schema, the description fully defines the return values (VERDICT, score, reasons). All parameters are covered, and the tool's complexity is addressed comprehensively. No gaps remain.

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 baseline is 3. The description adds significant value beyond the schema: it explains the 'deep' parameter in detail (live probe, slowness, graceful degradation) and provides an example email format. This elevates it above baseline.

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 starts with a clear verb+resource: 'Verify whether an email address is real and deliverable, live.' It enumerates specific checks and the verdict types, fully distinguishing it from the sibling tool 'verify_many' by focusing on single email verification.

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 explicitly states when to use this tool: 'before adding an email to a list, accepting a signup, or sending mail you don't want to bounce.' It implies the sibling tool is for batch verification, but does not explicitly provide when-not-to-use or alternative scenarios, though the context is clear enough.

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