Verify a single email address

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

With no annotations, the description carries the full burden and does reasonably well: it lists the checks run, states SMTP is opt-in and off by default for compliance, and notes the return shape (human summary plus structured data). It still omits rate limits, auth/permission needs, and what enabling SMTP actually risks.

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 tight sentences, front-loaded with the mechanism (DNS-based) and checks, then the key behavioral caveat. No wasted words.

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 3-param verification tool with full schema coverage and no output schema, the description covers mechanism, checks, the default/compliance behavior and the return format. The main gap is lack of sibling differentiation against verify_bulk, check_mx and is_disposable.

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 the schema already documents email, smtp and checks completely, including the smtp compliance note. The description adds nothing beyond that baseline, so a 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?

States a specific verb+resource ('email verification') and enumerates the concrete checks performed (syntax, MX, disposable, role). It reads clearly as a single-address verifier, but the description itself never differentiates from siblings is_disposable, check_mx and verify_bulk — only the title hints at 'single'.

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?

Usage context is implied (verify an email; SMTP off by default for compliance) but no when-to-use/when-not guidance and no routing to siblings like verify_bulk for batch work or check_mx for MX-only. The compliance caveat on SMTP gives partial practical guidance.

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