enrich_email

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

With no annotations, the description carries the full behavioral burden and does it thoroughly: it distinguishes syntax validity from MX presence from actual deliverability, explicitly notes that deliverability_checked is always false and likely_deliverable is always null, and discloses the DNS-over-HTTPS mechanism. This prevents the agent from over-trusting the result.

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 well-structured with summary, caveat, arguments, and return keys, and the most important scoping information is front-loaded. The return-key list is long, but it earns its place because there is no output schema.

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 two-parameter tool with no output schema and no annotations, the description covers inputs, outputs, a cost key, and a critical caveat. Minor gaps remain: semantics of similar return fields are not fully clarified, and error or network-failure behavior is not mentioned.

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 0%, so the Args section is essential and delivers: it gives a concrete email example and precisely explains check_mx's default behavior and effect. Both parameters are documented with meaning beyond the raw 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 opens with a specific verb and resource—'Validate and enrich an email address'—and elaborates with concrete behaviors: syntax validation, optional MX lookup, and disposable/free-provider flagging. The singular 'an email address' also makes clear this is a single-address tool, distinct from the batch sibling.

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 implies the tool is for validating individual email addresses and provides a useful caveat that MX presence does not guarantee mailbox existence. However, it never states when to prefer this tool over enrich_email_batch, validate_domain, or other sibling tools, and gives no exclusion criteria.

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