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

With no annotations, the description carries the full burden. It discloses that the tool checks syntax, MX records, and disposable status, which are meaningful behavioral details. However, it doesn't indicate whether MX checks involve network calls or how results are returned.

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, compact sentence that front-loads the verb and object, then lists the validation types in parentheses. Every word adds value, with no redundant content.

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 tool is simple (1 param), but no output schema or annotations exist. The description explains what is validated but not the return format or behavior on invalid emails, leaving the agent uncertain about outputs. This is a moderate gap.

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 provides only a parameter name 'email' and type string with no description (0% coverage). The description adds context that the value is an email address to be validated, but doesn't offer format constraints or examples, so it only partially compensates.

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 a specific verb ('Validate') and a clear resource ('email'), and goes further to specify the validation dimensions: syntax, MX, and disposable. This clearly distinguishes it from sibling tools like validate_domain or validate_phone.

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?

No explicit when or when-not guidance is provided. The description implies usage for validating email addresses, but doesn't mention alternatives like validate_domain or extract_emails, so the agent must infer from the tool name and sibling context.

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