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

Given no annotations, the description carries the full burden. It discloses the key behaviors: bulk operation, syntax checking, MX record lookup, SMTP probing, and disposable/role-based detection. It does not mention rate limits, response format, or potential latency, but for a verification tool, the behavioral profile is reasonably transparent.

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 sentences with zero wasted words. The first sentence states what the tool does, the second provides usage context. Information is front-loaded and scannable.

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?

The description covers purpose and usage but lacks information about the tool's output (return values) and any limitations (e.g., email volume limits). Without an output schema, the description should hint at what the agent receives, which it does not. The tool is simple, so the gap is moderate.

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 description coverage is 100%, so baseline is 3. The description does not add new meaning beyond the schema; it reiterates the checks but does not elaborate on parameter usage or constraints. The parameter semantics are adequately covered by 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 uses specific verbs and resources: 'Bulk-verify email addresses' and lists the types of checks (syntax, MX, SMTP, disposable, role-based). It clearly differentiates from sibling tools, none of which perform 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: 'before sending outreach' and the goal 'so you only contact addresses that actually exist.' It does not mention when not to use or alternatives, but the context is clear and sufficient for the tool's standalone purpose.

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